Timber Code

NZS 3603:1993

TIMBER STRUCTU RES

AMENDMENT NO. 4 (INCORPORATING AMENDMENT N0.3)

March 2005

CORRECTION AND REVISED TEXT

EXPLANATORY NOTE This amendment corrects errors in Amendment No.3 to NZS 3603:1993 (published 29 October 2004), incorporating all changes introduced by Amendment No.3.

Amendment No. 4 to NZS 3603 provides for lower design stresses for unverified timber. It recognizes deficiencies in sole reliance on visual grading as a means of reliably establishing the characteristic strength and stiffness properties of sawn timber.

Table 2.2 has been simplified so that there are only four grades for visually graded timber. Engineering grade has been deleted, as its availability is very limited (if at all) across New Zealand. The high 10.5 modulus of elasticity cannot be achieved by visual grading alone as it is well proven that visual grading cannot grade reliably for stiffness.

No.1 Framing is, as previously, visually graded to NZS 3631. No. 1 Framing that has been verified (now designated as VSG10, VSG8 and G8), has despite that verification had its bending, tension and compression strengths lowered to reflect the strength properties of the current and future crops. Compression parallel and shear strengths are seen as being representative of current and future crops. Studies by Forest Research show that lowering of these two strength properties has little effect on timber-framed structures built to meet NZS 3604. Lowering these strength properties will make it easier for a sawmill to achieve strength.

The grade stresses for Larch, Rimu, Kahikatea, Silver, Red and Hard Beech have been disestablished because these species are rarely used in new structures today. Larch, if used, can be bracketed with Radiata pine.

Table 2.3 has disestablished the use of the former F grades and replaced them with ‘MSG’ grades, the suite of which reflects the timber available on the market.

APPROVAL Amendment No. 4 (INCORPORATING AMENDMENT N0.3) was approved by the Standards Council on 24 March 2005 to be an amendment to NZS 3603:1993 pursuant to the provision of section 10 of the Standards Act 1988.

Related Documents (page 6) Add to NEW ZEALAND STANDARDS

NZS 3622:2004 Verification of timber properties (Amendment No.4 (INCORPORATING AMENDMENT N0.3), March 2005)

Add to AUSTRALIAN/NEW ZEALAND STANDARDS AS/NZS 4063:1992 Timber - Stress-graded - In-grade strength and stiffness evaluation

(Amendment No.4 (INCORPORATING AMENDMENT N0.3), March 2005)

Add new category: EUROPEANSTANDARD ENV 1995-1 -1 :1993 Eurocode 5: Design of timber structures. Part 1.1 : General rules and rules

for buildings (Amendment No.4 (INCORPORATING AMENDMENT N0.3), March 2005)

Copyright Standards New Zealand Provided by IHS under license with SNZ Licensee=Unitec Inst of Technology/5911177001

Not for Resale, 12/17/2006 19:36:50 MSTNo reproduction or networking permitted without license from IHS

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2 Clause 1.4 (page 1 1 ) Add new symbol in alphabetical order:

&, Lower bound modulus of elasticity parallel to the grain (Amendment No.4 (INCORPORATING AMENDMENT N0.3), March 2005)

Species

Radiata

Douglas fir

Radiata pine &

Douglas fir

pine &

Delete clauses 2.2.1, C2.2.1, 2.4.2, C2.4.2, table 2.2 and table 2.3 (pages 18 - 21) and substitute:

1. Moisture condition - Dry (m/c = 16 %) Grade Bending Compression Tension Modulus of Lower

strength strength strength elasticity bound fb fc f i E (GPa) modulus

of elasticity & (GPa)

VSG 1 O 20.0 20.0 8.0 10.0 6.7 VSG8 14.0 18.0 6.0 8.0 5.4 No 1 10.0 15.0 4.0 6.0 4.0

1 Framing 2. Moisture condition - Green' (m/c = 25 %)

G89 11.7 12.0 4.0 6.5 4.4 VSG10' VSG8'

Framing No 1 7.5 11 .o 3.0 4.8 3.2

1

2.2.1 Characteristic stresses and elastic moduli shall be as given in table 2.2 and table 2.3 for the appropriate species, grade and moisture conditions.

VSG10, VSG8, and G8 grades shall be obtained by verifying, in accordance with NZS 3622, timber which has, as a minimum, been visually graded as No.1 Framing to the requirements of NZS 3631.

c2.2.1 For the derivation of characteristic stresses for timber refer to AS/NZS 4063. The characteristic stresses shown in tables 2.2 and 2.3 for Radiata pine and Douglas fir are representative of most exofic pine species subject to verification where specified,

Table 2.2 - Characteristic stresses for visually graded timber (MPa)

NOTE - (1)

(2)

No.1 Framing is not verified and not subject to in-mill monitoring of strength and stiffness properties. No.1 Framing shall be graded to the requirements of NZS 3631. The green condition stresses and moduli values for the grades shown shall be used where the grades are used in service situations where the moisture condition may be 25 % or over (see 2.1.2). The durability requirements of NZS 3602:2003 must also be met.

Shear strength for dry Radiata pine shall be taken as f, = 3.8 MPa.

Shear strength for dry Douglas fir shall be taken as f, = 3.0 MPa.

Compression perpendicular to grain for dry Radiata pine and Douglas fir shall be taken as fp = 8.9 MPa Modulus of rigidity shall be taken as G = H15.

Shear strength for green Radiata pine shall be taken as f, = 2.4 MPa.

Compression perpendicular to grain for green Radiata pine shall be taken as fp = 5.3 MPa VSGIO and VSG8 are visual grades which have been verified in the dry condition. G8 is a visual grade which has been verified in the green condition.

(3)

(4) (5)

(6)

(7) (8) (9)



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Table 2.3 - Characteristic stresses for machine stress graded timber (MPa)

Species

Radiata pine &

Douglas fir

NOTE -

(1)

(2)

(3)

Shear strength for dry Radiata pine shall be taken as f, = 3.8 MPa. Shear strength for dry Douglas fir shall be taken as f, = 3.0 MPa. Compression perpendicular to grain for dry Radiata pine and Douglas fir shall be taken as fp = 8.9 MPa.

Grades shall be verified as required by NZS 3622.

2.2.1.1 Visually graded timber Visually graded timber shall be assigned the design parameters given in table 2.2 depending on whether it is verified or un-verified. Verified timber shall have its bending strength and stiffness (MoE) confirmed, and be identified, in accordance with the requirements of NZS 3622. Timbers not conforming to NZS 3622 shall be considered as un-verified.

2.2.1.2 Machine stress graded timber Machine stress graded timber shall have its properties verified, and be identified, in accordance with the requirements of NZS 3622.

2.4.2 Modulus of elasticity

2.4.2.1 General The modulus of elasticity used for the design of timber elements depends on the degree to which they are part of a system and therefore constrained to deformations similar to that of their neighbours.

2.4.2.2 For the design of timber elements within a system which constrains them to deformations similar to their neighbours and for which there are at least four elements in the system, the modulus of elasticity (,E) from table 2.2 or 2.3 shall be used.

C2.4.2.2 Joisted floors and timber-framed stud walls are examples.

2.4.2.3 For the design of timber systems which are not covered by clause 2.4.2.2, the modulus of elasticity shall be based on the values of E and Elb from table 2.2 or 2.3 as follows:

(a) Where the system consists of a single timber element the modulus of elasticity shall be Elb;

(b) Where the system consists of two or three elements acting together the modulus of elasticity shall be '/2 (E+ &).



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C2.4.2.3 An example of (a) would be a single element beam or lintel. An example of (b) would be a double elemenf beam or lintel such as where two 50 mm wide timber elements are used to make up a 1 O0 mm wide elemenf.

(Amendment No.4 (INCORPORATING AMENDMENT N0.3), March 2005)

O 2005 STANDARDS COUNCIL STANDARDS NEW ZEALAND

PRIVATE BAG 2439 WELLINGTON 6020



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NZS 3603:1993

TIMBER STRUCTURES STANDARD

AMENDMENT No. 2

July 1996

CORRECTION

EXPLANATORY NOTE

Amendment No. 2 gives the definitions for "y; in Equation C5 and Equation C7 in Appenduc C and .y: in Equation D3 in Appendix D revised by Amendment No. 1 to NZS 3603:1993.

APPENDIX C SLENDERNESS COEFFICIENTS FOR BEAMS

C2.3 Beams With no intermediate buckling restraints (page 11 6)

Under Eq. C5 delete the definition:

"h = height above centroid of the point of load application" and substitute:

"y,, = height above beam centroid of the point of load application".

(Amendment No. 2, July 1996)

C3 Continuously restrained beams (page 11 6)

Figure C1 - Continuously restrained beam

Delete Figure C1 and substitute new Figure C1.

4 Point of load application-o

Effectively lateral restraint

I--

Figure C l - Continuously restrained beam



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Column centroid -i+b~ - 3 Effectively continuous lateral restraint -, + --

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NZS 36031 993 2

d

APPENDIX D SLENDERNESS COEFFICIENTS FOR COLUMNS

D1 (page 118)

Under Eq. D3 add the definition:

'Ye - - distance from column centroid to point of load application'.

Figure D1 - Continuously restrained column

Delete Figure D1 and substitute new Figure D1.

Point oí j+l , axial load

Figure D1 - Continuously restrained column

(Amendment No. 2, July 1996) -__--------------------------------

Q 1996 STANDARDS COUNCIL STANDARDS NEW ZEALAND




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NZS 2403:1991

Code of practice for DEEP GEOTHERMAL WELLS

AMENDMENT No. 1

July 1996

CORRECTION

Clause 206.6.4 (page 29) Delete the equation for ft and substitute the following:

O 1996 STANDARDS COUNCIL STANDARDS NEW ZEALAND




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NEW ZEALAND STANDARD TIMBER STRUCTURES STANDARD

AMENDMENT No. 1

April 1996

NZS 3603:1993

m

EXPLANATORY NOTE - Amendment No. 1 incorporates technical and editorial changes, corrects notified and other typographical errors, and includes items by way of clarification.

APPROVAL .....................................

Amendment No. 1 was approved on 1 April 1996 by the Standards Council to be an amendment to NZS 3603:1993 pursuant to the provisions of section 1 O of the Standards Act 1988,

RELATED DOCUMENTS (page 6) -----------------------L-------------

NEW ZEALAND STANDARDS

Delete "NZS 3602:1990 Code of practice for specifying timber and wood-based products for use in building" and substitute "NZS 36û2:1995 Timber and wood-based products for us8 in building."

Delete "NZS 3606:1987' and substitute "'NZS 3606:1987 (to be superseded by AS/NZS 1328-oooO)."

Delete ""NZS 3614:1971 Spifikation for the manufacture of c o n s t d o n plywood."

Delete "NZS 361 5:1981 Specification for strength properties and design methods for construction plywood.'

AUSTRALIAIWNEW ZEALAND STANDARDS

Add "AS/NZS 1328-0000 Glued laminated structural timber (in preparation)"

Delete "AS/NZS 2269-0000 Structural plywood (in preparation)" and substituto:

"ASNZS 2269:1994 Plywood - Structural."

(Amendment No. 1, April 1996)

TITLE (page9) Delete "Code of practice for TIMBER DESIGN" and substitute "TIMBER STRUCTURES STANDARD".


1.4 Symbols (page 10) Deleto "AA, bearing area parallel to the grain" and substitute:

"A, bearing area for loading parallel to the grain."

(Amendment No. 1, April 1996) ~ ~~~~

1.4 Symbols (page 11) Add the following new definition:



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9.4 9.4

8.9

9.7 9.7

8.9

12.0 12.0

8.0

12.0 12.0

8.0

2 NZS 3603:1993

1.4 Symbols (page 12) Delete "& load sharing factor for laminated beams (clause 2.9)" and substitute:

"k, lamination factor (clause 2.9)" (Amendment No. 1, April 1996) __----------------------_--_--_----__

1.6 Construction review (page 16) Delete the text and substitute:

"All stages of construction of a structure or part of a structure to which this Standard is applied shall be adequately reviewed by a person who, on the basis of experience or qualifications, is competent to undertake the review."

(Amendment No. 1, April 1996) -----------------------------------__ Table 2.3 - Characteristic stresses for mechanically graded timber (MPa) (page 20) Delete table 2.3 and substitute new table 2.3. (Characteristic stress in tension parallel ( i t ) has been recalculated and new notes to the bottom of the table added).

Table 2.3 - Characteristic stresses for mechanically graded timber (MPa)

Grade Compression paraild

fe

Tension paraild

ft

Shoat in bOalVl8

4

Bending

?b

of das- *icuiar ticity

1. Graded dry to NZS 3618

Radiata

Douglas ir

F11 ~ 1 5 0 x 5 0 >15ox50

F6 (or No. 1F)

F11 5150x50 150x50

F6

33.9 30.4

17.7

33.0 29.8

17.7

16.9 15.2

8.8

16.5 14.9

8.8

4.1 4.1

3.8

3.2 3.2

3.0

28.6 27.1

20.9

30.1 28.3

22.1

2. Graded green to NZS 3618

> 150x50 17.1 15.9

12.7

19.8 18.3

14.5

13.3 11.3

7.4

13.3 11.3

7.4

2.7 2.7

2.5

2.5 2.5

2.3

26.6 22.7

14.8

26.6 22.7

14.8

I F6 (or No. 1F)

F11 s-150x50 > 150x50

F6

Douglas fir

5.0 9.3 5.0 8.7

4.7 6.5

3. Graded dry to AS 1748

30.1 24.8 19.5 15.3 12.1

20.6 16.2 12.7 10.2 8.1

3.7 3.1 2.5 2.1 1.8

Radiata

25.4 20.4

F5 16.2 12.1 7.9 12.1 6.9

NOTE - (1) Modulus of rigidity may be estimated from G = E115 (2) Modulus of elaskiîy in compression perpendicular to the grain may be estimated from E,, = 15/30,

(Amendment No. 1, April 1996) .....................................



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3 NZS 3603: 1993 Table 2.2 - Characteristic stresses for visually graded timber (MPa) (page 19) Delete table 2.2 and substitute new table 2.2. (Characteristic stress in tension parallel ( f i ) has been recalculated and new notes to the bottom of the table added).


1. Moisture condition - Dry (m/c = 16 %)

species

Radiata pine

Douglas fir

Rimu

Kahikatea

Silver beech

Red beech

Hard beech

2. Moisture condition

Grade

Engineering 1150x50 Engineering > 150x50 No. 1 Framing

Engineering s150x50 Engineering > 150x50 No. 1 Framing

No. 1 Framing

Building

Building

Engineering Building



Douglas fir

Rimu

Kahikatea

Silver beech

Red beech

Hard beech

NOTE -

Bending

fb

~

27.7

24.5

17.7

25.1

22.4

17.7

22.7

19.8

14.5

36.6 23.6

43.1 28.0

44.2 29.5

Green (m/c = 25 %)


Engineering á150x50 Engineering >150x50 No. 1 Framing

No. 1 Framing

Building

Building




22.7

20.1

14.8

22.7

20.1

14.8

15.0

15.0

13.9

32.3 20.7

38.1 25.1

42.8 28.3

hmpression ,aralld

fc

25.7

24.2

20.9

27.1

25.4

22.1

27.1

20.1

19.5

31.0 24.8

37.5 30.4

31.0 26.6

15.9

15.0

12.7

18.3

17.1

14.5

17.4

14.5

14.2

23.6 19.2

22.4 18.3

29.5 24.2

renrion iaralld

ft

13.8

12.2

8.8

12.5

11.2

8.8

11.3

9.9

7.2

18.3 11.8

21.5 14.0

22.1 14.7

11.3

10.0

7.4

11.3

10.0

7.4

7.5

7.5

6.9

16.1 10.3

19.0 12.5

21.4 14.1

Shear in beams

f,

3.8

3.8

3.8

3.0

3.0

3.0

3.5

3.8

3.0

3.5 3.5

5.3 5.3

5.0 5.0

2.4

2.4

2.4

2.4

2.4

2.4

2.7

2.7

2.4

2.7 2.7

3.8 3.8

4.4 4.4

>ompression mipen- ìicular

fP

8.9

8.9

8.9

8.9

8.9

8.9

8.9

10.9

5.9

7.1 7.1

12.4 12.4

14.2 14.2

5.3

5.3

5.3

4.7

4.7

4.7

5.6

6.0

4.4

3.8 3.8

7.7 7.7

10.6 10.6

(1) Modulus of rigidity may be estimated f m G =Ell 5. (2) For standard names of commercial timbers in New Zealand refer to NZS 3621. (3) Modulus of elasticity in compression perpendicular to the grain may be estimated from EP I €BO. (4) Grades shall bo specified with reference to NZS 3631 :1988.

Modulur Jf das- ticity E(GPa)

10.5

10.0

8.0

10.4

9.9

8.0

9.6

9.5

6.8

10.6 9.3

15.3 13.4

15.5 13.6

8.8

8.1

6.5

8.7

8.0

6.5

7.7

8.3

6.0

8.6 7.5

13.0 11.3

14.1 12.1



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4 NZS 3603:1993

Figure 2.2 - Parallel support system (page 24) In the note delete "glue laminated beams (see 8.7.2)" and substituto 'glue laminated members loaded in bending (see 8.7.2)'.

(Amendment No. 1, April 1996) .................................. Table 2.7 - Parallel support factor k, or k6 (page 25) Delete the title and substitute the following:

"Table 2.7 - Parallel support factor 16 or lamination factor &e"

(Amendment No. 1, April 1996) ..................................... Eq. 3.12 and the following definitions (page 36) Delete "Aj and substitute "A;.

(Amendment No. 1, April 1996) ..................................... 4.2.2.2 (page 45) In line 5 after the words "For directly loaded joints," add "with no in-plane moments,'.

In line 7 after the words "nominal strength" delete "can" and substltuto "shall'.

(Amendment No. 1, April 1996) ..................................... Eq. 4.3 (page 45) Delete 'U; and substitute "U;.


Figure 4.2 - Timber thickness and nail length (page 46) Delete the title and substitute new title "Timber thickness and depth of penetration for nails and coach screws".

.....................................

(Amendment No. 1, April 1996) ..................................... Eq. 4.7 (page 48) Delete "0; and substituto "Oc.

(Amendment No. 1, April 1996) ..................................... Eq. 4.9 (page 49) In the definitions delete "U, = charactertistic load given in table 4.6' and substitute:

"O& = characteristic strength given in table 4.7".

(Amendment No. 1, April 1996) ~

Table 4.10-Characteristic stnngth, ûsU(kN) for a single bolt in atwo-momkr joint in dry timber loaded parallel to the grain (page 55)

In the title delete "UsM" and substitute "QH" .




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NZS 3603:1993 5 Figure 4.4 - Characteristic strength for a bolt in a two-member joint in dry radiata pino or Douglas fir (page 54)

Delete figure 4.4 and substitute new figure 4.4.

Effective thickness (mml (Twice thickness of thinner member)

Figure 4.4 - Characteristic strength for a bolt in a two-member joint in dry radiata pine or Douglas fir

(Amendment No. 1, April 1996) _--_--_------------------------------ Copyright Standards New Zealand Provided by IHS under license with SNZ Licensee=Unitec Inst of Technology/5911177001


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Table 4.12 - Characteristic strength for a single bolt in dry timber loaded perpendicular to the grain

Under the heading Effective timber thickness 6,, aiîer the words "As for types 1,2 or 3" at the bottom of the table add "except that be is based on thickness of timber members only."

(page 56)


Table 4.1 3- Characteristic strength, Qskp(kN) for a single bolt in a two-member joint in dry timber loaded perpendicular to grain (page 57)

.....................................

In the title delete "Osb" and substitute "Qk,,"


4.4.3.2 (b)(2) (page 60) In line 2 delete "table 4.16" and substitute ïable 4.15".

(Amendment No. 1, April 1996) ..................................... 4.5.2 (b) Lateral baús (page 61) After the words "If the depth of penetration" add "shown in figure 4.2".


C5.2.4 (page 69) In line 8 delete "an over strength factor of l . M = 2.0 " and substitute "an over strength factor of 7,WØ = 2.0 '

(Amendment No. 1, April 1996) ..................................... C5.2.5 (page 71)

VH Y pH " and substitute "A5 = - GBt In Eq. 5.28 delete ' A 5 = - GBt

2 w 3 2VH3 + H e and substitute A7 =-+He In Eq. 5.30 delete A7 = -

3 €AB3 3EAB2

(Amendment No. 1, April 1996) ..................................... C5.2.5 (page 72) Delete the definition "P = inter storey shear force (N)".

Delete the definitions for 6, and stand substitute the following definitions:

"& = Vertical downward movement (mm) at the base of the compression end of the wall (this may be due to compression perpendicular to grain deformation in the bottom plate) Vertical upward movement (mm) at the base of the tension end of the wall (this may be due to deformations in a nailed fastener and the members to which it is anchored)".

¿$ =



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7

6 PLYWOOD (page 73)

NZS 3603:î 993

C6.1.1 Delete "AS/NZS 2269 is a new joint New Zealand-Australian Standard expected to be published in December 1993 (to supersede NZS 3674) " and substitute:

"AWNZS2269 is a Joint Australian/NewZealand Standardpublishedin 1994 (to supersede NZS 36 1 4) ".

(Amendment No. 1, April 1996) --------------------------------__-__ 6.5.1.1 Bending strength (Eq. 6.1 O ) (page 79) Delete "b = stability factor given in 6.6.5" and substitute:

"k, = stability factor given in 6.6.4"

(Amendment No. 1 April 1996) ..................................... 6.5.1.2 Tension strength (Eq. 6.1 1) (page 79) Delete "Nnt= nominal rolling shear strength" and substitute "N,, = nominal tensile strength".

(Amendment No. 1, April 1996) ..................................... 6.6.4.4 Stiffeners in web beams (page 84) In line 5 delete "design shear (V,)," and substitute "design shear (# Vni),"


6.6.7.2 Load capacity of a jointed interface (page 86)

In Eq. 6.31 delete "Qn, = kQkwl / O w kQknZt O II and substitute "Onsi = s c

In the definitions delete "U0 = 2 / 3 M and substitute "UQ = 2d3".

and add the following new definitions:

"n = number of rows of nails" and

I'W = contact width for glued joint"


7.2 Characteristic stresses and elastic moduli (page 87) In line 5 in (a) delete the words "outer density" and substitute "outer zone density".


Table 7.1 - Characteristic stresses (MPa) and modulus of elasticity (GPa) for naturally round softwood timber in green condition (page 87) In the column for "f," delete "16l and substitute "21". In the column for "(,'I delete "7.7" and substitute "9.0' and delete "6.4" and substitute "8.8".

.....................................

Add the following note to the bottom of the table "NOTE - The outer zone density is the basic density (oven dry weightholume in green condition) in the outer 20 ?'O of the radius of the pole."


8.7.1.1 (page 91) In line 4 delete "parallel support factor," and substitute "lamination factor,"



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SNZ NZSx3603 93 8583169 0063966 958

8

8.7.2.1 (page 91) In line 4 delete "parallel support factor," and substitute "lamination factor,".

NZS 3603:1993

(Amendment No. 1, April 1996) ----------c--------------_------- - 8.7.2.2 (page 91) In line 3 delete "k," and substitute "k;.

(Amendment No. 1, April 1996) ----------c--------------------------

C9.5.5 (page 103) In Eq. 9.3 delete "(d- 2t32" and substitute "(d- t,J2'.

In Eq. 9.4 delete "-1.92 t,2 and substitute "-1.29 t:". (Amendment No. 1, April 1996) ----------------------------------__-

C10.6.1 (page 106) In line 1 delete "kiS" and substitute nk32*.

(Amendment No. 1 , April 1996) -----------------------------------__ APPENDIX B LATERAL AND TORSIONAL BUCKLING RESTRAINTS

83.2 Force on lateral restraints (page 1 12)

Delete Eq. B8 and substitute I F A = k33k34k35 d(n, + 1) ' 0 .1M~

0 .05M~ Delete Eq. B9 and substitute " F A = k33k34k35 d(n, + 1)'

(Amendment No. 1, April 1996) ..................................... B4.2 Torque on torsional restraints (page 11 3)

(Amendment No. 1 , April 1996)

APPENDM C SLENDERNESS COEFFICIENTS FOR BEAMS

C2.2 Beams with intermediate buckling restraints (page 1 14)

c5

Lay Delete Eq. C3 and substitute ME = -[@)Y GJr'l

(Amendment No. 1, April 1996) ..................................... C2.2 Beams with intermediate buckling restraints (page 1 15)

( m y y

(€0, Delete the definition " a = 1 - - .



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SNZ NZSx3603 9 3 8583169 00bL9b7 8 9 4

9 NZS 3603:1993 Table C1 - Coefficients for slenderness factor of bisymmetrical beams with intermediate buckling restraints (page 115)

In the first column delete "Moment parameter b" and substitute "Moment parameter p"

(Amendment No. 1, April 1996) ------------------------------------_ C2.3 Beams with no intermediate buckling restraints (page 116)

Delete Eq. C7 and substitute Io M, =

(Amendment No. 1. April 1996) ..................................... APPENDIX D SLENDERNESS COEFFICIENTS FOR COLUMNS

D i


APPENDIX E DEFORMATION AND DISPLACEMENT MODULUS OF MECHANKALLY FASTENED JOINTS (page 119)

.....................................

E l

Delete '= 2,0.5 for bolted joints with holes drilled 1.5 mrn oversize,' 3

3 and substitute *= 2n0.5 for bolted joints with holes drilled 1.5 rnm oversize".

1 Delete 'F for split-ring connectors or shear plates."

1 and substitute ' for split-ring connectors or shear plates."




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- ~

SNZ NZS*3b03 9 3 8583369 00bLîbB 720 =

10 NZS 3603:1993

APPENDIX G DESIGN OF PLYWOOD PANELS SPANNING IN TWO DIRECTIONS (page 124) Table G1 - Maximum length to width (Uw) ratios for plate bending action in plywood

Delete the heading "Across width, w" and substitute "Along width, w"

Table G2 - Formulae for plywood plates spanning in two directions Under the heading "Central point load"

Delete "A = C s S P d / € I ~ and substitute "A = C,SPw31€IwLu

in the definitions for Appendix G Aíter the words "L = span of panel (between joists or blocking)" add '(always the longest direction)"

Aíter the words " w = span of panel at right angles to L direction" add "(always the shortest direction)"


Q 1996 STANDARDS NEW ZEALAND PRIVATE BAG 2439, WELLINGTON 6001



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TIMBER STRUCTURES STANDARD

Superseding NZS 3603:1990 and NZS 361 31981

UDC 691.1 1 : 624.04 : 69.01

Pr KK



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SNZ NZSr3603 9 3 m 8583169 0010782 840 m

No Date of issue

NZS 3603: 1993

Description

COMMITTEE REPRESENTATION

This Standard was prepared bythe P3603A Timber Design Cornmittee for the Standards Council under the Standards Act 1988.

The Timber Design Committee consisted of the following persons:

Andrew Buchanan, University of Cantebury (Chairman) Tony Bryant, University of Auckland Andrew King, Building Research Association of New Zealand Pat Simperingham, Carter Holt Harvey Timber Limited Peter Smith, Spencer Holmes Miller Partners Limited Robert Tan, Gang Nail NZ Limited Bryan Walford, Forest Research Institute Limited

ACKNOWLEDGEMENT

The special assistance given to the Timber Design Committee by Hank Bier, Forest Research Institute Limited and Richard Hunt, University of Auckland is gratefully acknowledged.

Extensive use has been made of AS 1720.1 Timber Structures Code in the writing of this document and permission to use this material is also gratefully acknowledged.

O COPYRIGHT

The copyright of this document is the property of the Standards Council. No part of it may be reproduced by photocopying or by any other means without the prior written permission of the Chief Executive of Standards New Zealand unless the circumstances are covered by the exemption sections (19 and 21) of the Copyright Act 1962.

STANDARDSNEWZEAIAND 6TH FLOOR, WELLINGTON TRADE CENTRE,

(Private Bag 2439, Wellington 6020) Telephone: 0-4-384 21 08 Fax: 0-4-384 3938

181 - 187 VICTORIA STREET, WELLINGTON 6001.

AMENDMENTS Entered by, and date



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SNZ NZSr3b03 93 8583Lb9 0030783 787

NZS 3603:1993

CONTENTS PAGE

Committee representation ......................................................... IFC Acknowledgment ....................................................................... IFC Related documents ........................................................................ 6 Foreword ....................................................................................... 8

Section 1 General

1.1 Scope .................................................................................... 9 1.2 Interpretation ......................................................................... 9 1.3 Definitions ............................................................................. 9 1.4 Symbols .............................................................................. 10 1.5 Design ................................................................................. 15

Construction review .............................................. , ............. 16 Materials and workmanship ................................................ 16

1.6 1.7

Section 2 Stresses and elastic moduli for sawn timber

2.1 General ............................................................................... 17

2.3 2.4 2.5

2.7 2.8 2.9

2.2 Characteristic stresses ........................................................ 18 Properties of timber species not listed ................................ 20 Basis of design .................................................................... 21 Strength reduction factors ................................................... 21

2.6 Secondary stresses ............................................................ 22 Modification factors, kl and k2 for duration of load ............. 22 Modification factor, k3 for bearing area ............................... 23 Modification factors, k4, k5 and kf3 for load sharing ............ 25

2.1 O Modification factor, k8 for stability ....................................... 26 2.1 1 Temperature effects ............................................................ 27 2.1 2 Earthquake effects .............................................................. 28

Section 3 Design of structural members

3.1 General ............................................................................... 30 3.2 Beam design ....................................................................... 30

Tension member design ..................................................... 38 Combined bending and compression ................................. 39 Combined bending and tension .......................................... 40

3.3 Column design .................................................................... 36 3.4 3.5 3.6

Section 4 Joints

4.1 General ............................................................................... 41 4.2 Nails .................................................................................... 42

4.4 Bolts .................................................................................... 50 4.5 Coach screws ..................................................................... 61

Other mechanical fasteners ................................................ 62

4.3 Screws ................................................................................ 47

4.6 4.7 Glued joints ......................................................................... 63

Section 5 Design of special structures

5.1 Timber decking ................................................................... 65 Shear walls and diaphragms ............................................... 67 5.2

Contents continued overleaf

1



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NZS 3603:1993

Section 6 Plywood

6.1 General ............................................................................... 73 6.2 Stresses and moduli ........................................................... 73 6.3 Modification factors ............................................................. 74 6.4 Loading perpendicular to the plane of the sheet ................. 77 6.5 6.6 Plywood components .......................................................... 81

Loading in the plane of the sheet ........................................ 79

Section 7 Round timbers

7.1 General ............................................................................... 87 7.2 Characteristic stresses and elastic moduli .......................... 87 7.3 Design ................................................................................. 87 7.4 Modification factor, k20 for trimming or shaving .................. 88 7.5 Modification factor, k21 for preservative treatment

involving steaming .............................................................. 88 7.6 Modification factor, k22 for dry use conditions .................... 88 7.7 Effective sections ................................................................ 88

Section 8 Glued laminated timber

8.1 Scope .................................................................................. 89

8.3 Standard sizes .................................................................... 89 8.4 Finish .................................................................................. 90 8.5 Moisture content ................................................................. 90 8.6 Design ................................................................................. 91 8.7 Modification factors ............................................................. 91 8.8 Curved and tapered members ............................................ 93 8.9 Butt joints ............................................................................ 97 8.10 Camber ............................................................................... 99 8.1 1 Holes drilled in fabricated members .................................... 99 8.1 2 Nail plate joints .................................................................... 99

8.2 Specification ........................................................................ 89

Section 9 Design for fire resistance

9.1 Scope ................................................................................ 100 9.2 Fire resistance ratings ....................................................... 100 9.3 Loads ................................................................................ 100 9.4 Calculation of fire resistance rating of timber elements .... 100 9.5 Details of construction ....................................................... 102

Section 10 Testing of timber structures

10.1 General ............................................................................. 104 10.2 Testing authority ............................................................... 104 10.3 Testing conditions ............................................................. 104 10.4 Test procedure .................................................................. 105 10.5 Acceptance criteria ........................................................... 106 10.6 Prototype or sample testing .............................................. 106 10.7 Proof testing ...................................................................... 107 10.8 Reporting of tests .............................................................. 108

Contents continued

2 Copyright Standards New Zealand Provided by IHS under license with SNZ Licensee=Unitec Inst of Technology/5911177001


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NZS 3603: 1 993

Table

2.1

2.2 2.3

2.4 2.5 2.6 2.7 2.8 3.1 4.1 4.2 4.3

4.4

4.5

4.6

4.7

4.8 4.9

4.10

4.1 1 4.12

4.1 3

4.14

4.15

4.16

5.1 6.1 6.2 6.3 6.4 7.1

Condition to be assumed for determination of characteristic stresses. modulus of elasticity. joint design and dimensions ....................................................... 18 Characteristic stresses for visually graded timber (MPa) .... 19 Characteristic stresses for mechanically graded timber (MPa) ....................................................................... 20 Duration of load factor. kl for strength ................................ 22 Duration of load factor. k2 for deflection ............................. 23 Bearing area factor. ........................................................ 23

Stability factor. ....................................................................... 27 Notch coefficient. .................................................................. 34 Classification of timber species for joint design .................. 41 Minimum spacing of nails and screws in joints ................... 44 Characteristic strengths (N) for one plain steel wire nail

Characteristic withdrawal strength per millimetre of nail penetration (N/mm) for one plain steel wire nail in side grain .................................................................................... 47 Characteristic strength (N) for one steel wood screw in

Maximum design withdrawal strength for one steel screw in dry timber ........................................................................ 50 Characteristic withdrawal strength per millimetre of screw thread penetration (N/mm) for wood screw inserted

Parallel support factor. or ........................................... 25

in single shear in side grain in dry timber ............................ 46

single shear in side grain in dry timber ............................... 49

at right angles to the grain of dry timber ............................. 50 Values of fqfor bolted joints in dry timber .......................... 52

loaded parallel to the grain .................................................. 53 characteristic strength for a single bolt in dry timber

Characteristic strength, Q, k/ (kN) for a single bolt in a two-member joint in dry timber loaded parallel to the grain .................................................................................... 55

Characteristic strength for a single bolt in dry timber

characteristic strength, Qskp (kN) for a single bolt in a two-member joint in dry timber loaded perpendicular to grain .................................................................................... 57 Factor, kl2 for bolt and coach screw joints in

Factor, kl3 for the design of multiple-bolt and

Characteristic withdrawal strength per millimetre of penetration of thread (N/mm) for a coach screw in

Values of fpjfor bolted joints in dry timber .......................... 56

loaded perpendicular to the grain ....................................... 56

green timber ........................................................................ 60

multiplecoach-screw joints ................................................. 60

dry timber ............................................................................ 62 Maximum nail diameters (mm) ............................................ 69 Characteristic stresses for structural plywood .................... 74 Face grain orientation factor, k15 for strength ..................... 76 Face grain orientation factor, kl6 for stiff ness .................... 76 Face grain orientation factors for shear .............................. 77

in green condition ................................................................ 87

Characteristic stresses (MPa) and modulus of elasticity (GPa) for naturally round soflwood timber

Contents continued overleaf



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S N Z NZS*3b03 9 3 8583169 8010786 496 E

NZS 3603:1993

7.2 Peeling or shaving factor. k20 ............................................. 88 7.3 Steaming factor. k21 .................................................................. 88 7.4 Dry use factor. k22 ..................................................................... 88 8.1 Laminated members - standard widths .............................. 90 8.2 Minimum radius of curvature ............................................... 90 8.3 Size factor for beams and tension members ...................... 93 8.4 Values of constants for calculation of radial stresses in

pitched beams ..................................................................... 95 10.1 Compensation factor, b o ....................................................... 107 10.2 Compensation factor, ....................................................... 107 10.3 Sampling factor, /(32 ................................................................ 107 10.4 Likely values of coefficients of variation ............................ 108 c1

c2

E l G1

G2 G3 H1 H2

J1

J2 J3

Coefficients for slenderness factor of bisymmetriicai beams with intermediate buckling restraints ..................... 115 Coefficients for slenderness factors of bisymmetrical beams with no intermediate buckling restraints ................ 117 Duration of load factor. k37 ............................................... 120 Maximum length to width (UM ratios for plate bending

Formulae for plywood plates spanning in two directions .. 124

Stablity factor, for compression .................................... 126 Maximum width to thickness (w/f) ratios for plywood

Percentages of plywood design strength transmitted across scarf joints ............................................................. 128 Minimum overall length of splice plates for glued joints .... 129 Percentages of design strength transmitted across

action in plywood .............................................................. 124

Values of constants, G to C7 inclusive ............................ 125

panels stable in compression ............................................ 127

spliced butt joints .............................................................. 129

Figure

2.1 2.2 2.3 2.4 3.1 3.2 3.3 3.4 3.5 4.1 4.2 4.3 4.4

4.5 5.1 5.2 5.3

6.1 6.2 6.3

Length of bearing surface (rnm) .......................................... 24

Grid system ......................................................................... 26 ka factor .............................................................................. 27 ka for beams - dry timber ................................................... 32 ka for beams - green timber ............................................... 32 Notation for a notch ............................................................. 34 Graph for factor, kg ............................................................. 35 Effective length factor, k10 ........................................................ 37

Eccentric joints .................................................................... 52

Parallel support system ....................................................... 24

Positioning of fasteners ....................................................... 43 Timber thickness and nail length ........................................ 46

Characteristic strength for a bolt in a two-member joint in dry radiata pine or Douglas fir ............................................. 54 Graph of Hankinson formula for stresses and loads ........... 59 Types of decking lay-up for floors and roofing .................... 66 Shear flow in a panel sheathed shear wall or diaphragm ... 68 Distribution of loading for horizontal diaphragm and

Moisture content factor, k14 ..................................................... 75 Critical sections in some plywood components .................. 82 Stiffener spacing for plywood webs in flexural

shear wall system ............................................................... 69

components ........................................................................ 85

Contents continued

4



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SNZ NZS+3b03 93 8 5 8 3 1 b î 0030787 322 R

NZS 3603: 1993

8.1 Determination of k25 factor for pitched beams .................... 94 8.2 9.1 Radius of arris rounding .................................................... 101 B1 Intemediate restraints ...................................................... 111 C1 Continuously restrained beam .......................................... 116 D1 F1

Appendix

Simple span tapered beams ............................................... 97

Continuously restrained column ........................................ 118 Dimensions and nomenclature used in Appendix F .......... 121

A

B C D E

F

G H J

The determination of characteristic strengths for metal fasteners for timber ........................................................... 109 Lateral and torsional buckling restraints ........................... 111 Slenderness coefficients for beams .................................. 114 Slenderness coefficients for columns ............................... 118 Deformation and displacement modulus of mechanically fastened joints ............................................. 119 Method of computing effective section properties of plywood ............................................................................. 121 Design of plywood panels spanning in two directions ....... 124 Local buckling of plywood elements in compression ........ 126 Design of end or edge joints in plywood ........................... 128



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NZS 3603:1993

RELATED DOCUMENTS

Reference is made in this document to the following:

NEW ZEALAND STANDARDS

NZS 3601 :1973 NZS 3602:1990

NZS 3604:1990

NZS 36051 992 NZS 3606:1987 *NZS 361 4:1971

NZS 361 5 1 981

NZS 3618: - - - - Part 1:1984

Part 2:1984 NZS 3621 A987

NZS 3631 :1988 NZS 4203:1992

NZMP 9:1989

NZMP 3640: 1992

Metric dimensions for timber Code of practice for specifying timber and wood- based products for use in building Code of practice for light timber frame buildings not requiring specific design Timber piles and poles for use in building The manufacture of glue laminated timber Specification forthe manufacture of construction

Specification for strength properties and design methods for construction plywood Mechanical stress grading of timber Specification for the mechanical stress grading of timber Rules for mechanical stress grading of timber Standard names of commercial timbers in New Zealand New Zealand national timber grading rules Code of practice for general structural design and design loadingsfor buildings (known as the Loadings Standard) Fire properties of building materials and elements of structure Specification of the minimum requirements of the New Zealand Timber Preservation Council Inc.

PlyWood

AUSTRALIAN/NEW ZEALAND STANDARDS

AS/NZS 1530.4-1 990 Fire-resistance test of elements of building construct ion

AS/NZS 2269-0000 Structural plywood (in preparation) AS/NZS 4063:1992 Timber-stress-graded - In-grade strength and

stiffness evaluation

AUSTRALIAN STANDARDS

AS 1649-1974

AS 1720-

Methods for the determination of basic working loads for metal fasteners for timber Timber structures (known as SAA timber structures code)

Part 1-1988 Design met hods AS 1748-1978 Mechanically stress-graded timber AS 2754- Adhesives for timber and timber products

Adhesives for plywood manufacture Part 1-1 985

To be superseded by joint AS/NZS Standard (in preparation)

6



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NZS 3603: 1 993

OTHER DOCUMENTS

CAN 3-086-MM Engineering design in wood (working stress design) Forest Research Institute: Forest Products Division Report FP/TE 28 and Forest Products Laboratory Report FP/TE 99 (unpublished)

NZNSEE Bulletin, Vol. 19, No 2 June 1986, “Horizontal Timber Diaphragms for Wind and Earthquakes”, Smith, Dowrick and Dean.

Proceedings, 1988 International Conference on Timber Engineering, Seattle, USA, pages 251 -256 “Moment Resisting Nail Plate Joints”, R Hunt and A H Bryant.

The New Zealand Building Code Handbookand Approved Documents (NZBC).

Timber Use Manual. New Zealand Timber Industry Federation.

American Institute of Timber Construction Manual.

US Department of Agriculture, Report FPL 34

University of Canterbury, Report CE 8911

RELATED LEGISLATION

Building Act 1991 Engineers Registration Act 1924

The users of this Standard should ensure that their copies of the above-mentioned New Zealand Standards, overseas and referenced Standards are the latest revisions or include the latest amendments. Such amendments are listed in the annual Standards New Zealand Catalogue which is supplemented by lists contained in the monthly magazine Stanobrdsissued freed charge tocommitteeandsubscribing members of Standards New Zealand.

7



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SNZ NZSJ3b03 73 8583169 0010770 917

NZS 3603:1993

FOREWORD

This Standard sets out the requirements for the design of timber buildings and building elements. This edition is a soft conversion of NZS 3603:1990, which was in the working stress design format, into a limit states design format. The intention is to give the same design solutionsfor most cases, ¡.e. it is calibrated toexisting practices, so that existing relativities are maintained. Eventually it is expected that adjustments will be made on the basis of reliability analyses to achieve consistent levels of performance between differing materials, load types and building types.

In recent years in-grade testing has provided a means of establishing characteristic stresses for building timbers and, where sufficient information is available, stress levels have been set on this basis rather than as previously derived from the testing of small clear specimens.

Other significant changes in this edition include the introduction of a section on fire resistance (from the Standards New Zealand MP 9 publication, with minor changes) and a section on plywood design (superseding NZS 361 5, with major changes). The design stresses for glue laminated timber are now derived from sawn timber stresses, using the same methods as in AS 1720.1.

REVIEW OF STANDARDS

Suggestions for improvement of this Standard will be welcomed. They should be sent to the Chief Executive, Standards New Zealand, Private Bag 2439, Wellington 6001.



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S N Z N Z S * 3 b 0 3 93 8583167 0010771 8 5 3

NZS 3603: 1993

NEW ZEALAND STANDARD

Code of practice for TIMBER DESIGN

1 GENERAL

1.1 Scope

1.1.1 This Standard sets out requirements for methods of design of timber elements of buildings, and is approved as a verification method for NZBC compliance.

1.1.2 This Standard applies specifically to sawn timber, glue laminated timber, natural round timber and construction plywood.

1.2 Interpretation

1.2.1 In this Standard the word “shall” indicates a requirement that is to be adopted in order to comply with the Standard, while the word “should indicates a recommended practice.

1.2.2 Subject to 1.2.1, clauses prefixed by “C” are intended as comments on the corresponding mandatory clauses.

1.2.3 The full titles of reference documents cited in this Standard are given in the list of “Related Documents” immediately preceding the Foreword.

1.3 Definitions For the purpose of this Standard, unless inconsistent with the context, the following definitions apply:

BACK. Back means the outermost veneer on the opposite side from the face of a plywood sheet.

CHARACTERISTIC STRESS or CHARACTERISTIC STRENGTH. For strength properties, characteristic stress or strength is an estimate of the lower 5-percentile value determined with 75 % confidence, from tests on a representative sample of full size test specimens. For stiffness properties, the characteristic value is the mean value.

DESIGN ENGINEER. A person who, on the basis of experience or qualifications, is competent to design structural elements of the building under consideration to safely resist the design loads or effects on the building.

DURATION OF LOADING. The period during which a member, a structural element, or a complete structure is stressed as a consequence of the loads applied.



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NZS 3603: 1 993

EFFECTIVE SECTION PROPERTIES. Section properties parallel to the face grain of plywood where the reduced contribution of plies perpendicular to the face grain have been taken into account.

FACE. The outermost veneer on the better side of a plywood sheet.

PANEL SHEAR. Shear through the thickness of a plywood sheet, such as that associated with racking resistance.

PLY (PLIES). A layer of veneer (veneers) in a plywood sheet.

PROOF TESTING. The testing of any one unit to ascertain the structural adequacy of only that one unit tested.

PROTOTYPE TESTING. The testing of one or more units (or structures or elements) to ascertain the structural adequacy of units which are to be manufactured nominally equal or better in both quality of materials and workmanship to those tested.

ROLLING SHEAR. Shear in the plane of the plies across the grain causing fibres to roll on one another.

SAMPLE TESTING. The testing of a sample of units (or structures, or elements) randomly selected from an existing set.

SEASONED (or DRY) STATE or CONDITION. The condition of a piece of wood when the maximum moisture content anywhere within it does not exceed 18 %.

STRENGTH REDUCTION FACTOR. A factor that takes into account the uncertainty in the prediction of resistance.

STRENGTH:

NOMINAL STRENGTH. The nominal strength (equivalent to the ideal strength in NZS 4203:1992) is the product of the characteristic stress or strength, those modification factors appropriate to the service conditions and relevant section properties.

DESIGN STRENGTH. The design strength (equivalent to the dependable strength in NZS 4203:1992) is the product of the characteristic stress or strength, the strength reduction factor, those modification factors appropriate to the service conditions and relevant section properties.

1.4 Symbols In this Standard, symbolsshall have the following meanings, provided that othersymbols, or other meanings for symbols listed below, that are defined immediately adjacent to formulae or diagrams, shall apply in relation to those formulae or diagrams only:

a minimum bolt spacing perpendicular to the grain

A cross-sectional area of a member

AI bearing area parallel to the grain

Ap

As shear plane area

bearing area perpendicular to the grain

Aw area of washer



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SNZ NZSx3603 93 = 8 5 ô 3 3 b î 0030793 626

NZS 3603: 1993

b

be

bn

d

da

dn

dP

d S

E

f

G

I

J

K

~

breadth of a member (perpendicular to direction of flexural loading)

effective timber thickness in a bolted joint

length of a notch in a rectangular member

depth of a member (in direction of flexural loading)

diameter of a fastener

net depth of a member at a notch

mean diameter of a pole

depth of a member less the distance from the unloaded edge to the centre of a bolt

modulus of elasticity parallel to the grain

characteristic stress

fb

fc

fci

b fpb

bc fpi

Ipp

fpr

bs bf fs characteristic shear stress

fsh characteristic shear stress in plywood

ft characteristic stress in tension parallel to the grain

f characteristic stress at an angle to the grain

modulus of rigidity

moment of inertia

polar moment of inertia

displacement modulus of a joint

characteristic extreme fibre stress in bending parallel to the grain

characteristic stress in compression parallel to the grain

characteristic bolt bearing stress parallel to the grain

characteristic stress in compression perpendicular to the grain

characteristic bending stress of plywood

characteristic compression stress of plywood in the plane of the sheet

characteristic bolt bearing stress perpendicular to the grain

characteristic compression stress of plywood normal to the plane of the sheet

characteristic rolling shear stress of plywood

characteristic panel shear stress of plywood

characteristic tension stress of plywood



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NZS 3603: 1 993

product of modification factors

duration of load factor for strength (clause 2.7)

duration of load factor for deflection (clause 2.7)

bearing area factor (clause 2.8)

parallel support factor (clause 2.9)

grid system factor (clause 2.9)

load sharing factor for laminated beams (clause 2.9)

notch coefficient (table 3.1)

stability factor (clause 2.10)

distribution coefficient for concentrated load on a grid system (clause 3.2.7)

effective length factor for columns (clause 3.3.2)

bolt bearing stress factor (clause 4.4.2)

k12 factor for the design of bolted or coach-screwed joints in green timber (clause 4.5.2)

k13 factor for the design of multiple-bok and multiple-coach-screw joints (clause 4.4.3)

k14

k15

k16

k17

kl8

kl9

k20

k2 1

k22

k23

moisture content factor of plywood (clause 6.3.3)

face grain orientation factor for strength of plywood (clause 6.3.5)

face grain orientation factor for stiffness of plywood (clause 6.3.5)

stress concentration factor for rolling shear in plywood (clause 6.3.6)

plywood panel shear framing support factor (clause 6.3.7)

bending strength factor for 3-ply plywood (clause 6.4.1)

modification factor for trimming or shaving of natural round timber (clause 7.4)

modification factor for preservative treatment involving steaming (clause 7.5)

dry use factor for naturally round timber (clause 7.6)

factor to allow for curvature of laminations (clause 8.7.5)

k24 size factor (clause 8.7.7)

k25 factor for determination of radial stress in pitched cambered beams (clause 8.8.2)

k26, k27, k28 factors for determination of radial stress in pitched cambered beams (clause 8.8.2)

k29 factor for butt joints in the tension zone of beams (clause 8.9.2)

k o factor for effect of duration of test loading on strength of special components (clause 10.6.2)



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h1 factortocompensateforthefactthatthetest loading isnot of 15 minduration (clause 10.6.2)

k32 sampling factor for prototype or sample testing (clause 10.6.2)

k33, k34, k35 factors for determination of buckling restraint effects (Appendix B)

k36, k37 factors for determining deformation of joints (Appendix E)

L span of member as a beam, or column length

Lm distance between points of restraint against lateral movement normal to the x-x axis

Lay distance between points of restraint against lateral movement normal to the y-y axis, or between points of rotation restraint

Ls spacing of web stiffeners (clause 6.6.4)

M bending moment

M* bending moment for strength limit state

MI in-plane bending moment of a plywood sheet for strength limit state

MX bending moment about the X-X axis for strength limit state

M i bending moment about the Y-Y axis for strength limit state

Mn nominal bending strength

M,i nominal in-plane bending strength of plywood (clause 6.5.1)

Mnx nominal bending strength about the X-X axis

Mny nominal bending strength about the Y-Y axis

N* direct force for strength limit state

N i bearing load for strength limit state

N i axial compression load for strength limit state

N; axial tensile load for strength limit state

Nnb nominal bearing strength

Nnb/ nominal bearing strength for bearing parallel to the grain

Nnbp nominal bearing strength for bearing perpendicular to the grain

Nncx nominal compressive strength for buckling about the X-X axis

Nncy nominal compressive strength for buckling about the Y-Y axis

Nnt nominal tensile strength

Nnb nominal bearing strength for bearing at angle to the grain

n number of members or fasteners



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longitudinal stress for tapered beams

transverse stress for tapered beams

shear stress for tapered beams

tensile stress at a butt joint

shear stress at a butt joint

applied load or force

Euler buckling load

penetration of a fastener

applied shear as a percentage of the design shear (clause 6.6.4.4)

section property of plywood panel or component in shear

characteristic strength

characteristic strength of a bok loaded parallel to the grain

Qkp characteristic strength of a bolt loaded penpendicular to the grain

0,

Qnsi nominal strength of a joint in a plywood component

Qsk system characteristic strength of a bolted joint

Qsk/ system characteristic strength of a bolt loaded parallel to the grain

as@ system characteristic strength of a bolt loaded perpendicuular to the grain

nominal strength of a joint

strength limit state design shear flow

radius of curvature

design load effect on a joint

slenderness coefficient

SI slenderness coefficient for a beam

S2, FQ slenderness coefficients for a column

spacing of members or fasteners

thickness of plywood

thickness of charring

effective timber thickness of plywood

lamination thickness



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SNZ N Z S t 3 6 0 3 9 3 8583369 0030797 273

NZS 3603: 1 993

limit state load from NZS 4203

shear force for strength limit state

design shear force for rolling shear

design panel shear force for plywood

nominal shear strength

nominal panel shear strength of plywood

nominal rolling shear strength of plywood

load per unit length applied in bending or width of a plywood panel

section modulus

net section modulus of plywood

net section modulus of a charred beam

slope of the upper surface of a tapered member

deflection

strength reduction factor (clause 2.5)

angle between the direction of load and the direction of grain

displacement ductility factor for a building

coefficient of variation

1.5 Design

C1.5 NZS 4203 specifies general design requirements, design loads, design load combinations, and deformation requirements. This Standard specifies characteristic properties and methods for determining design strengths for timber structures.

Because the strength properties of timber are time-dependent, this Standard takes account of load duration in a manner different from that used in NZS 4203. It is important, therefore, to recognize that the design load combinations specified in NZS 4203 are to be determined in accordance with load components as specified in NZS 4203, which allows for the low probability that loads of brief duration will act concurrently with other non-permanent loads. Design strengths are to be determined in accordance with this Standard, which allows for the effect that the duration of load has on the material strength, regardless of the probability of a particular load combination.

This Standard has been written on the assumption that it will be used for design purposes by qualified professional engineers with some knowledge and experience of the specialised techniques necessary for the design and construction of timber buildings.

1 S.1 Except as provided by 1.5.3 timber buildings and parts of buildings shall be designed in accordance with the “limit state” method of design specified in NZS 4203.



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SNZ NZS*3603 93 8583169 0010796 108

NZS 3603: 1 993

c1.5.1 Clause 7.5.1 does not prevent the design of buildings to suitable non-specific design codes (e.g. NZS3ôo.4).

1 S.2 Timber structural members shall be proportioned so that the design actions are less than design strengths determined in accordance with this Standard.

1.5.3 Timber buildings or parts of buildings may be test loaded as specified in section 10 of this Standard, and if such testsdemonstratethat theconstruction is adequate for its intended purpose it shall be accepted as complying with this Standard.

C1.5.3 Structures or parts of structures designed in accordance with this Standard are not required to be tested unless by agreement between fhe parties concerned. Tests may be accepted as an alternative to calculation or may became necessary in circumstances which include:

(a) Where a structure orpariof a structure is not amenable to sufficiently accurate calculation

(b) Where materials or design methods are used other than those of the relevant specification or code of practice

(c) Where there is doubt or disagreement as to whether the structure or some part of if complies with design rules, or as to whether the quality of the materials used is to the required Standard.

1.6 Construction review All stages of construction of a structure or pari of a structure to which this Standard is applied shall be adequately reviewed by either a suitably qualified professional engineer (or his nominated representative) or a building certifier or a representative of the Territorial Authority.

1.7 Materials and workmanship The relevant requirements of NZS 3602 shall apply subject to the requirements of this Standard.



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SNZ N Z S S 3 6 0 3 93 m 8583369 0030797 044 m

NZS 3603: 1 993

2 STRESSES AND ELASTIC MODULI FOR SAWN TIMBER

2.1 General

2.1.1 In the determination of design strengths, timber shall be assumed to be in the dry condition or in the green condition according to its moisture content at the time of fabrication, installation, or in service as shown in table 2.1 and as required by 2.1.2 and 2.1.3.

2.1.2 When timber not exceeding 100 mm thick is graded, fabricated, and installed at a definable moisture content between 18 % and 25 % and will not exceed that moisture content in service, the characteristic stress (see 2.3) may be obtained by linear interpolation between the values for green and for dry timber. For the purpose of interpolation “dry“ shall be taken to mean 16 % moisture content and “green” to mean 25 % moisture content. In such cases dimensions shall be assumed to be dry dimensions (see 3.1.2).

C2.7.2 Stresses for the dry condition refer to an annualaverage moisture confent of 76 %, which by reference to NZS 3602 implies a maximum of 18 %.

2.1.3 Timber that is graded, fabricated, or installed at a misture content exceeding 25 % but that will have a moisture content in service not exceeding 18 % may only be regarded as item 2 of table 2.1 provided that:

(a) The timber shall not exceed 50 mm thick and

(b) The full design load shall not be applied before the timber has dried to a moisture content not exceeding 18 %; and

(c) Loads due to dead load, erection procedures, and any other loads imposed before the timber has dried to a moisture content not exceeding 18 % shall not cause the green condition design strength to be exceeded.

C2.1.3 If item 2 of table 2.1 is used, the designer shouid:

(a) Take special precautions to ensure that the moisture content and loading conditions assumed in design are achieved in practice;

(6) Allow for enhanced bending creep deflections during drying under dead load;

(c) Aliow for the effects of shrinkage on dimensions and on joints.



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SNZ NZSa3603 9 3 W 8583169 0010800 696

NZS 3603: 1 993

gauged with an allowance for shrinkage, or dry dressed, as appropriate

Table 2.1 - Condition to be assumed for determination of characteristic stresses, modulus of elasticity, joint design and dimensions -

Item

1.

2.

3.

- 4.

-

Condition when gradad, fabricated, or installed

Green (see alsa 2.1.2)

Green (see also 2.1.2and2.1.3)

Dry (see also 2.1.4)

Dry (see also 2.1.4)

Condition in service

Green (¡.e. wet or damp

conditions) SeNilX

Dry (¡.e. dry service conditions)

Dry (¡.e. dry

conditions) S0NiCe

wet (i.0. wet or damp conditions)

Condition for determination of characteristic stresses and modulus of elasticity tables 2.2 and 2.3

Green

Dry except for shear in Douglas fir which shall be green

Dry

Dry for modulus of elasticiiy Green for stresses

Condition for joint and fastening design

Green gauged

Green

Dry

Green

Cross section dimensions to be used for design (or actual measured dimension) I

'It may be assumed thatcross section dimensions of unrestrained members will reduce by25 % as the moisture content changes from 25 % to 16 %.

2.1.4 Members exceeding 1 O0 mm thick, unless built up from thinnertimbers, shall be assumed to have a moisturecontent exceeding 1 8 %at the time of installation unless proved otherwise by a special investigation.

2.1.5 On-site structural gluing shall not be permitted except in accordance with 4.7

c2.1.5 Structural gluing, particularly with rigid adhesives, requires proper attention to moisture content, temperature, pressure, surface preparation and other factors for satisfactory performance of the gluedmembers. These conditions may be difficult to achieve with on-site gluing operations.

2.2 Characteristic stresses

2.2.1 Characteristic stresses and elastic moduli shall be as given in tables 2.2 and 2.3 for the appropriate species, grade, and dry or green condition.

c2.2.1 Refer to Forest Research Institute documents for derivation of characteristic stresses for timber, The characteristic stresses shown in table 2.2 for radiata pine are representative of most exotk pine species and macrocatpa.

18



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SNZ NZSa3603 'i3 = 8583Lb'i OOLO801 5 2 2 m

NZS 3603:1993


1. Moisture condition - Dry ( d c = 16 %)

species

Radiata pine

Douglas fir

Larch

Rimu

Kahikatea

Silver beech

Red beech

Hard beech

Grade



No. 1 Framing

Building

Building




Bending

fb

27.7

24.5

17.7

25.1

22.4

17.7

22.7

19.8

14.5

36.6 23.6

43.1 28.0

44.2 29.5

2. Moisture condition - Green (míc = 25 %)

Compression parallel

fe

25.7

24.2

20.9

27.1

25.4

22.1

27.1

20.1

19.5

31.0 24.8

37.5 30.4

31 .O 26.6

Radiata pine

Douglas fir

Larch

Rimu

Kahikatea

Silver beech

Red beech

Hard beech

Engineering I 1 5 0 x 50 Engineering ~ 1 5 0 x 5 0 No. 1 Framing


No. 1 Framing

Building

Building




22.7

20.1

14.8

22.7

20.1

14.8

15.0

15.0

13.9

32.3 20.7

38.1 25.1

42.8 28.3

15.9

15.0

12.7

18.3

17.1

14.5

17.4

14.5

14.2

23.6 19.2

22.4 18.3

29.5 24.2

Tension parallel

ff

16.5

14.8

10.6

15.0

13.6

10.6

13.6

11.8

8.6

21.8 14.2

26.0 16.8

26.6 17.7

13.6

11.8

8.9

13.6

11.8

8.9

8.9

8.9

8.3

18.9 12.4

22.7 15.0

25.7 17.1

Shear in beams

fs

3.8

3.8

3.8

3.0

3.0

3.0

3.5

3.8

3.0

3.5 3.5

5.3 5.3

5.0 5.0

2.4

2.4

2.4

2.4

2.4

2.4

2.7

2.7

2.4

2.7 2.7

3.8 3.8

4.4 4.4

NOTE - (1) Modulus of rigidity may be estimated from G =U15. (2) For standard names of commercial timbers in New Zealand refer to NZS 3621.

Compression perpendicular

fP

8.9

8.9

8.9

8.9

8.9

8.9

8.9

10.9

5.9

7.1 7.1

12.4 12.4

14.2 14.2

5.3

5.3

5.3

4.7

4.7

4.7

5.6

6.8

4.4

3.8 3.8

7.7 7.7

10.6 10.6

Modulus of elasticity E (GPa)

10.5

10.0

8.0

10.4

9.9

8.0

9.6

9.5

6.8

10.6 9.3

15.3 13.4

15.5 13.6

8.8

8.1

6.5

8.7

8.0

6.5

7.7

8.3

6.0

8.6 7.5

13.0 11.3

14.1 12.1



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~

SNZ NZSa3b03 93 = 8583367 0030802 467

Shear in beams

f*

4.1 4.1

3.8

3.2 3.2

3.0

Compression perpendicular

fP

9.4 9.4

8.9

9.7 9.7

8.9

2.7 2.7

2.5

2.5 2.5

2.3

5.9 5.9

5.3

5.0 5.0

4.7

1 26.6 22.7

NZS 3603:1993

Table 2.3 - Characteristic stresses for mechanically graded timber (MPa)

Bending Compression parallel

fc

Tension parallel

f

Modulus of elasticity E (GPa)

1. Graded dry to NZS 3618

Radiata

Douglas fir

F i l á150x50 > 150x50

F6 (or No. 1 F)

F i1 5150x50 > 150x50

F6

33.9 30.4

17.7

33.0 29.8

17.7

28.6 27.1

20.9

30.1 28.3

22.1

20.3 18.2

10.6

19.8 17.9

10.6

12.0 12.0

8.0

12.0 12.0

8.0

2. Graded green to NZS 3618

Radiata F11 5150x50 >15Ox50

17.1 15.9

12.7

19.8 18.3

14.5

15.9 13.7

8.9

15.9 13.7

8.9

9.2 8.7

6.5

9.3 8.7

6.5

F6 (or No. 1 F)

F11 s150x50 > 150 x 50

14.8

Douglas fir

26.6 22.7

F6 14.8

3. Graded dry to AS 1748

Radiata or Douglas i¡ r

F14 F11 F8 F7 F5

41.3 32.5 25.4 20.4 16.2

30.1 24.8 19.5 15.3 12.1

21.1 16.6 13.0 10.3 8.2

3.7 3.1 2.5 2.1 1.8

12.1 12.1 12.1 12.1 12.1

12.0 10.5 9.1 7.9 6.9

NOTE - Modulus of rigidity may be estimated from G = ,515

2.2.2 Characteristic stress in compression at angles to the grain other than Oo and 90" shall be calculated from the Hankinson formula:

(Eq. 2.1) ..................................................................... fcfp

fc sin2 8 + f p cos2 e f* =

where B is the angle between the direction of the load and the direction of the grain (see also figure 4.5).

c2.2.2 The characteristic stresses given in table 2.2 are, with the exception of fb and E for radiata pine, obtained from the results of testing of small clear specimens of timber in the standard 20 x 20 mm dimension and in both the green and air-dry condition. For radiata pine in bending, the characteristic stresses are obtained from the results of tests on structural sized beams.

2.3 Properties of timber species not listed Timber of species and grades not listed in tables 2.2 and 2.3 may be assigned characteristic stresses on the basis of evidence establishing the stresses at the 5 % exclusion limit and elastic moduli based on mean values.



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SNZ N Z S x 3 6 0 3 9 3 = 8583169 0010803 3T5

NZS 3603: 1 993

C2.3 For species listed in AS 1 720 but not included in table 2.2, the stress values given in AS 1 720 for the visualgrade concernedmaybe used. Forhrdnatedveneerlumber (L VL) Characteristic stresses should be determined as in AS/NZS 4063 (a newjoint Standad).

2.4 Basis of design

2.4.1 For the strength limit state all membfrs shall be proportioned so that the design strength, $Rn, is not less than the design action, S , ¡.e.

S * I @Rn ........................................................................ (Eq. 2.2)

C2.4. i For example, the design strength in bending is $Mn

where

Ø = strength reduction factor Mn = nominal strength of the member in bending, given by:

Mn = k f b Z ......................................................................................................... (Eg.2.3)

where

k = product of the relevant modification factors such as fhose in 2.6 to 2.72 inclusive that are appropriate to the particular service conditions for which the structural member is being designed

fb = characteristic stress in bending given in tables 2.2 or 2.3, Z = section modulus about the axis of bending.

2.4.2 Themodulusof elasticityasdeterrninedfromtable2.2or2.3or6.1 or7.1 shall be usedfordesign except as provided by 2.7.2, 5.1.2, 7.4, 7.5, 7.6 and 8.7.6.

C2.4.2 The values of modulus of elasticityare the average values of those measured during tests. Deflection of members made from Visually graded radiata timber from some South Island forests may be 1 U % greater than those calculated using the modulus of elasticity from the table. Due consideration of this should be made when the precise deflection is important.

2.5 Strength reduction factors The strength reduction factor, @, has values as follows:

for timber, poles and glulam, for nails in lateral loading for toothed metal plate connectors for other types of fasteners

for actions derived from the strength of ductile

fp = 0.8 @ = 0.8 $= 0.8 $= 0.7

for plywood $I = 0.9

elements under large displacements fp= 1.0 design for fire resistance @ = 1.0

C2.5 The value of $ = 7. O applies to the seismic design of components of ductile structures, where the actions are unlikely to increase even if larger displacements are imposed.



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~

S N Z NZS*3b03 93 ö583169 0010804 231 =

Dead and live loads that are essentially permanent such as stores (including water tanks and the like), library stacks, fixed plant, soil pressures.

Snow loads, live loads, crowd loadings, concrete formwork, vehicle, pedestrian and cattle loadings.

NZS 3603: 1 993

0.60

0.80

2.6 Secondary stresses

Wind, earthquake, impact, erection and maintenance loadings, pile driving

C2.6 Careful consideration should be given to possible secondary stresses. Where these cannot be reduced to negligible proportions, suitable provisions in the design should be made,

1 .o0

2.7 Modification factors, ki and k2 for duration of load

2.7.1 The Characteristic stresses of timber elements and characteristic strengths of fasteners (see section 4, Joints) shall be multiplied by the value of kl from table 2.4 corresponding to the load of shortest duration in the total design load combination being considered.

All possible combinations of loads shall be checked using the appropriate value of kl for each combination.

c2.7.1 In deciding the value of kl appropriate to a particular bad, designers will need to consider not only the actual duration of application but also the frequency of repeatedapplications and the chance of design loadings being exceeded.

Subject to these considerations, the durations listed in table 2.4 may be interpreted as: Permanent: exceeding five years Medium: Brief: not exceeding six hours.

six hours to five years

Table 2.4 - Duration of load factor, kl for strength

Duration of load

Permanent

Medium

Brief

Examples I k’

2.7.2 Effect on deflection Allowance for creep effects on long-term deflection shall be made by multiplying the calculated elastic deflection due to each part of the load by the value of k2 corresponding to the duration of that part and the moisture content of the member at the time of loading as shown in table 2.5. Values of k2 for intermediate moisture contents and intermediate load durations may be obtained by linear interpolation.

C2.7.2 When troubles are experienced with timber beams, it is frequently because insufficient provision has been made for the additional deflections that occur with time under dead bad, particularly when the timber was initially green. Such creep effects in timber are heavily

22



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SNZ NZSm3603 93 D 8583169 0010805 178

NZS 3603:1993

Duration of load

influenced by changes in moisture content (particularly the initial drying) rather than by time. Because this concept is foreign to most designers, and because moisture content change takes time, the procedure of 2.7.2 has been adopted. Designers should appreciate that in such cases as:

Moisture For bending, For tension content at time of loading

compression or shear

(a) Timber that is kept continuously wet (e.g. retaining walls);

Length of bearing 10 25 surface (mm)

1.90 1.60 k3

(b) Timber that has a large cross section (say exceeding 85 mm thick); or

50 75 1 O0 150

1.30 1.15 1 .o6 1 .o0

(c) Timber that is dry initiallx as in glued laminated timber

creep deflections will be less than is experienced in the usual use of sawn timber to which 2.7.2 particularly applies.

Small dimension members, less than about 100 mm thick, may creep more than indicated by factor k2 in table 2.5 if they are periodically wet and dry in service, as is the case with members exposed to the weather.

Table 2.5 - Duration of load factor, k2 for deflection

12 months or more

12 months or more

2 weeks or less

25 % or more

18 %or less

Any

3.0

2.0

1 .o

1.5

1 .o

1 .o

2.8 Modification factor, For bearing surfaces less than 150 mm long (measured parallel to the grain) which are not less than 75 mm from the end of the member under consideration, the characteristic stress in compression perpendicular to the grain, 6 shall be multiplied by the value of /Q in table 2.6 for the length of bearing surface shown in figure 2.1. For circular washers, the length of the bearing surface shall be taken as the diameter of the washer.

for bearing area

23



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SNZ NZSs3603 93 m 8583369 00L080b 004 m

NZS 3603: 1 993

Length for t h e d e s i g n of t h e jo is t

Length of bearing for t h e d e s i g n of

Figure 2.1 - Length of bearing surface (mm)

s u r f a c e t h e jo is t

Bolts with timber c o n n e c tors b e t w e e n m e m b e r s

Load applied through very stiff e l e m e n t

T h e number of laminations in t h e s h a d e d a r e a shall be used for calculating t h e parallel support f a c t o r for glue laminated b e a m s (see 8.7.2)

Figure 2.2 - Parallel support system



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SNZ N Z S * 3 6 0 3 73 = 8583167 OOL0807 T 4 0 =

Number of elements 2

k4or k6 1.14 1.20

NZS 3603: 1 993

2.9 Modification factors, q, and for load sharing

3 4 5 6 7 8 9 l o o r more

1.24 1.26 1.28 1.30 1.31 1.32 1.33

C2.9 Structural systems with load sharing between elements have less vanabihîy than individual elements. This is accounted for in design by the use of the k4 factor (for parallel support systems), the k5 factor (for grid systems), or the k6 factor for ghe laminated beams.

2.9.1 Parallel support systems For support systems of two or more elements that are effectively connected so that all of the elements are constrained to the same deformation (see figure 2.2) the characteristic stresses shall be multiplied by the value of k4 corresponding to the number of elements as shown in table 2.7. The factor 14; is used to account for load sharing in glue laminated beams as described in section 8.

C2.9. I The values of k4 and k6 given in table 2.7 are derived from:

1 - 1.65 vn-0.5 k4 = ke =

1 - 1.651) ................................................................. (Eq. 2.4)

where

n = number of elements v = coefficient of variation, assumed to be 19.5 %.

2.9.2 Grid systems Forsupportsystemsofthreeormore bending membersortrussesactingtogether (see figure 2.3) to support either:

(a) An overlaying set of members (usually laid at right angles to the supporting members); or

(b) A sheathing material having significant bending stiffness,

in determining the design strength, the characteristic stresses for bending, fb, bearing, f p , and shear in beams, fs shall be multiplied by the value of k5 given by:

................................................................... (Eq. 2.5)

but not less than 1 .O0

where

k4 =

S = the centre-to-centre spacing of the supporting members

LB = the span of the supporting members.

the value obtained from 2.9.1 that would be applicable if the main beams were fastened together to act as a parallel support system



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SNZ NZSx3603 7 3 8583167 0010808 987

NZS 3603:1993

C2.9.2 Clause 3.2.7can be used to determine whether the sheathing system hassignificant bending stiffness. No increase in design strength due to the effect of load sharing shall be permined for concentratedloads, but the effective load on the loaded member may be reducedas given by 3.2.7.

Beam

All beams loaded n Crossing members

Figure 2.3 - Grid system

2.10 Modification factor, for stability In the design of beams and columns, the characteristic stresses in bending, fb , and in compression parallel to the grain, fc , shall be multiplied by the value of ka corresponding to Sas shown in table 2.8 or figure 2.4 where Sis the maximum value of slenderness coeff icient as given by 3.2.5 for bending or 3.3.3 for axial compression. Linear interpolation shall be used for intermediate values of S.

c2.10 The k8 - S relationship Mn be expressed as a formula:

for S = 70 to 25 ks = al + aZS + a3S2 + a4S3

where a2 a3 a4 a5 a6

-1.933 0.21 u. 775 -D. U 7 7 6 7/5000 235.5 -1.937

al k8 green 0.45 U. 1237 -0. U082 7/7500 251.4

k8 dry

26



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SNZ NZS+3b03 93 m 85831b î 0010809 813 m

NZS 3603: 1993

5

70 75 80 85 90 95

Table 2.8 - Stability factor kjj

1. Green

k8

0.068 0.060 0.052 O. 046 0.041 0.037

S

5

70 75 80 85 90 95

up to 10 15 20 25 30 35

k8

0.063 0.055 0.048 0.043 0.038 0.034

2. Dry

S

up to 10 15 20 25 30 35

k8

1 .o0 0.91 0.71 0.50 0.36 0.27

S

40 45 50 55 60 65

k8

0.21 0.1 6 0.1 3 0.1 1 0.093 0.079

1 .o0 0.90 0.67 0.46 0.33 0.25

40 45 50 55 60 65

0.1 9 0.15 0.12 0.10 0.085 0.072

2.1 1 Temperature effects Timber exposed to elevated temperatures shall be the subject of a special study.

C2.17 Under normal conditions in Ne wzealand, no modification to the characteristic stresses need be made for the effects of temperature. The effect of elevated temperatures on timber may be temporary or permanent depending on the actual temperature reached, the humidity of the surrounding atmosphere, and the length of time the conditions are applied, For example, . under conditions of relative humidity of 85 %, an 8 % tempraty loss in strength for each 7 O *C rise in temperature above 20 O C can occur andpermanent loss in strength can occur above 65 *C. For temperature effects on poles during treatment see 7.5.

1.0

0.9

0.8

0.7

0.6

o 0.5 L o

rr>

c

L

y" 0.4

0.3

0.2

0.1

O O 10 20 30 40 50 60 70 80 90 100

Slenderness coef f i c ien t S Figure 2.4 - k8 factor



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SNZ NZSa3603 93 8583369 001OB10 535

NZS 3603: 1 993

2.12 Earthquake effects

2.12.1 Design forces Design forces resulting from earthquakes shall be calculated by rational analysis using the loads specified in NZS 4203, considering the potential for ductile behaviour, the possible modes of failure, and the lateral stiffness of the structure. For structures required to be ductile, allowance shall be made for any increases in internal forces which may occur under large displacements.

C2.72.7 Stiff ness Earthquake forces are sensitive to the stiffness of the structure under lateral loads because the stiffness influences the natural perids of vibration. All factors influencing the stiflness should be assessed. Because timber structures are relatively flexìble (compared with concrete or steel structures), non-structural components such as partitions or exterior cladding may make a significant contribution to the overall stiffness. On the other hand, connections between timber members often permit considerable movement due to inifial slackness or compression perpendicular to the grain, which can reduce the overall stiffness,

Modes of failure A principal objective of earthquake resistant design is to prevent sudden failure when a structure experiences large displacements, It is desirable to design structures to avoid a brittle fracture which could resuk in a sudden loss of strength. For structures which are likely to fail in a brittle mode, increasing the reserve strength reduces the possibility of failure under earthquake loading. For ductile structures it is more important to ensure that the chosen ductile mechanism can occur as intended.

2.12.2 Design strength For structures subjected to earthquake loading all components shall be proportioned and detailed such that the design strengths of members and fastenings are not exceeded, using the appropriate modification factors listed in this Standard.

2.12.3 Capaciîy design

2.12.3.1 All structures designed for ductile or limited ductile response shall be designed using a capacity design procedure.

2.12.3.2 The process of capacity design shall be based on a selected yield mechanism which can allow large displacements of the structure without significant loss of strength. The design of all Components shall be such that the selected mechanism is able to occur without premature failure in another mode.

2.12.3.3 All components not designed as yielding elements shall be proportioned such that their dependable strength is not exceeded when subjected to the increased forces resulting from lateral displacements of p times those when the design forces are applied, where p is the displacement ductility factor used to determine the design forces.

2.1 2.4 Structures designed for elastic response Structures which are not capable for exhibiting ductile behaviour shall be designed for elastic response. All components shall be designed to resist the design forces obtained from NZS 4203 using a structural ductility factor of no more than 1.25.

C2.72.4 The following types of structures are generally not capable of exhibiting ductile behavbuc * Structures with all connections so strong that failure can OcCuT as a wood failure in

bending oraxial tensbn. Most glue-laminatedportal frames with nailedplate connections



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SNZ NZSx3603 93 8583369 0030833 V ï 1 D

NZS 3603: 1 993

are in this category unless the connections are specially designed for ductility. Structures with rigid glued connections. Structures which could fail as a result of local perpendkular-to-grain tension stress. Structures which rely on light steel strap diagonal bracing. Structures with the weakest point being non-ductile connections such as toothplates or large diameter bolts.

* * *

A structural ductility factor of 1.0 should be used for structures which are likely to fail in a sudden brittle mannerand which have no significantpotential for load sharing between la feral load resisting elements.

A structuraldudility factor of I .25 may be used if there is potential forload sharing, or if there is some inherent ductility in the members or connections.

2.12.5 Structures designed for ductile response For structures designed for ductile response, the ductile members or connections shall be designed to resist the design forces obtained from NZS 4203 using a structural ductility factor of no more than 4.0. All othercomponentsshall be subjected to capacity design procedures to resist the increased forces resulting from lateral displacements of p times those when the design forces are applied.

C2.12.5 Ductile structures Ductile structures are those designed and detailed to ensure that the chosen ductile mechanism can allow large displacements of the structure without significant loss of strength. The following can be designed as ductile structures:

* Shearwalls or diaphragms with nailed sheathing. Chord members and foundation hold- down connections must have sufficient strength to ensure that the sheathing nailsare the weakest part of the structure. Structures with timber-to-timber connections using nails or small diameter bolts. The strength of the connections must not exceed the likely strength of the timber. Structures with well detailed nailed steel plate connections where the connection strength at large displacements does not exceed the likely strength of the timber. Structures with thin nailplate connections where large displacements can occur as a result of wood crushing and nailplate buckling,

*

*

Calculation of the increased forces resulting from large deflections require information about the expected load-displacement relationship for the structure.

Where ductility is achieved through nail slip in timber shearwalls or diaphragms, the increased forces are given in 5.2.4.

2.1 2.6 Structures designed for limited ductile response For structures designed for limited ductile response, the ductile members or connectionsshall be designed to resist the forces obtained from NZS 4203 using a structural ductility factor of no more than 3.0.

C2.12.6 Limited-ductile structures Limited-ductile structures are an intermedia te category which exhibit some ductiliîy, but not sufficient for large inelastic displacements to be relied upon with certain@. This categoty includes structures listed above as ductile, but where the ability to undergo large inelastic displacements is less certain.

In many cases there willbe little advantage in a limitedductile design compared with an elastic design, because the large overstrength factors in nailed structures may result in similar member sizes for the two design methods.



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SNZ NZSx3603 93 8583169 0010812 308

NZS 3603: 1 993

3 DESIGN OF STRUCTURAL MEMBERS

3.1 General

3.1.1 Thissection appliesto thedesignoftimber structural membersotherthan thoseof naturally round timber (see section 7, Round timbers, see also 1.5).

c3.1.1 Although this sectbn applies to structural members of any cross section, the most commn design case of a rectangular member is treated in detail. For design requirements specific to plywood see section 6. Special structures such as bridge decking and arches are dealt with in section 5, Design of special structures.

3.1.2 All engineering design calculations shall be based either on the minimum cross section dimensionsappropriate to conditions listed in table2.1 or theactual dimensions. Thedimensions applicable for a particular call dimension are those listed in NZS 3601.

c3.1.2 for rough sawn timber, call dimensions may be appropriate.

3.1.3 For the purpose of calculating the strength of a member at any section the effective net crosssection shall be taken as the cross section less due allowance for the reduction in area caused by all features such as sinkings, notches, bolts or screw-holes, mortices at that section or within a distance either side of the section equal to twice the larger cross-sectional dimension of the member.

3.2 Beam design

3.2.1 General In the calculation of the strength (see section 2, Stresses and elastic moduli for sawn timber) and deformation (see section 2 and NZS 4203) of a beam, due regard shall be paid to the beam's effective span and lateral stability. See also 3.5 for combined bending and axial loading, and Appendix B for the design of lateral and torsional restraints.

3.2.2 Effective spans The effective span of a flexural member shall be taken as the distance between the centres of areas of bearing, provided that with a member extending over bearings longer than is necessary, the effective span may be measured between centres of bearing lengths that would be adequate according to this standard. The effective span of a cantilever is the cantilever length plus half the required bearing length.

C3.2.2 Due attention should be paid to the eccentricity of the load on the support member when advantage is taken of the proviso to 3.2.2.

3.2.3 Flexural shear strength

3.2.3.1 The flexural shear strength of an unnotched rectangular section shall satisfy:

v* I r$V" ........................................................................ (Eq. 3.1)



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SNZ NZSS3b03 73 m 8583Lb9 OOLOBL3 244 m

NZS 3603: 1 993

where

@Vn = design strength of the member in shear @ = strength reduction factor V* V, = nominal strength of the member in shear.

= design shear force produced by the strength limit state design loads

The nominal strength of a member in shear shall be taken as

........................................................................ (Eq. 3.2) vn = kl W 5 f . s

where

kl to k5 = modification factors given in section 2 fS = characteristic stress in shear AS = shear plane area (for rectangular beam loaded about its major axis in bending,

As = 2bd3 where b equals the breadth and d equals the depth of the beam).

3.2.3.2 When calculating the design shear force, V*, in a beam, loads lying within a distance from the inside face of a suppori of 1 .O times the depth of the beam may be disregarded except in the application of 3.2.6.

3.2.4 Strength in bending The bending strength of an unnotched beam shall satisfy

M* I @Mn ........................................................................ (Eq. 3.3)

where

@Mn = design strength of the member in bending + = strength reduction factor M* M, = nominal strength of the member in bending.

= design bending moment produced by the strength limit state design loads

The nominal strength for a beam shall be taken as

Mn = kl k4k5 k 8 f b z ........................................................................ (Eq. 3.4)

where

kl , k4, k 5 = modification factors given in section 2 k8

fb Z

= stability factor as defined in 3.2.5. For a rectangular beam, ka can be obtained directly from figure 3.1 or 3.2.

= characteristic stress in bending = section modulus of the beam about the axis of bending (for rectangular beams Z= bd2/6, where b equals the breadth and dequals the depth of the beam).



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~

S N Z NZSx3603 93 13583369 0010814 L B O

NZS 3603: 1 993

Length - breadth ratio lay/b

Figure 3.1 - l~ for beams - dry timber

Length - breadth ratio Lay/b

Figure 3.2 - ØQ for beams - green timber



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SNZ NZS83b03 93 = 8583169 0010815 O13 W

NZS 3603: 1 993

3.2.5 Slenderness coefficient for lateral buckling

3.2.5.1 The slenderness coefficient for lateral buckling of beams shall be as defined in 3.2.5.2 and 3.2.5.3 or as defined in Appendix C (which gives the general case and certain specific cases), and shall not exceed 85 for beams loaded by wind or earthquake loads only or 50 for all other beams. The slenderness coefficient shall be used to obtain k8 as described in 2.10.

3.2.5.2 For an end-supported solid beam of rectangular cross section the Slenderness coefficient, S1 shall be taken as follows:

Si = 1.35 - [ [ d r -irr .......................................................................... (Eq. 3.5) b b

where Lay is the distance between points of restraint against lateral movements of the compression edge. Alternatively, the stability factor k8 may be obtained directly from figures 3.1

and 3.2.

3.2.5.3 For an end-supported solid beam of rectangular cross section that is continuously restrained against lateral displacement of the tension edge the slenderness coefficient, SI shall be taken as:

......................................................................... (Eq. 3.6) d b

s, = 3-

3.2.6 Strength of notched beams A beam of rectangular cross section notched on the tension edge as shown in figure 3.3 shall be so proportioned to satisfy

M* dn -

v+ 1.2 - < 1 .5 Ø k , k k 5 b f & , .......................................................................... (Eq. 3.7)

where

design bending moment produced by strength limit state design loads design shear force produced by strength limit state design loads net depth of the member at notch strength reduction factor modification factors given in section 2 notch coefficient given in table 3.1 characteristic shear stress 2bdn/3 for a notched rectangular beam where b equals the breadth of the beam.

33



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SNZ N Z S * 3 6 0 3 9 3 = 8583369 0030836 T53 M

Notch slope

bn/a

O

2

4

NZS 3603: 1993

k7

a2O. ld acO.1d

3. O 1. o do. 5 a0.5 - -

2.6 1.1 60.33 a0.33

2.2 1.3 d0.25 a0.25

lb t

Figure 3.3 - Notation for a notch

3.2.7 Effective concentrated loads on beams in grid systems The effective concentrated load on a beam that is a supporting member in a grid system (see 2.9.2) shall be taken as ks times the actual concentrated load on an overlying member or the structural sheathing material where:

1 + 144a + 448a2 5 + 272a + 448a2

kg =

This formula is plotted in figure 3.4

and

........................................................................ (Eq. 3.8)

........................................................................ (Eq. 3.9)

where

y = 1 .O for a simply supported beam y = 0.72 for a beam continuous over two equal spans

and

E&, E ~ C = flexural rigidity of the beam and crossing members respectively Ls, L c = span of beam and crossing members respectively n = total number of crossing members



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1.0

0.9

0.8

0.7

0.6

0.5

0.3

0.2

0.1

O O 0.001 0.01 0.1 1 10 100

af

Figure 3.4 - Graph for factor, kg

3.2.8 Built-up beams In built-up beams such as I-beams, Cbeams or box-beams, design stresses in timber flanges shall not exceed the values that would be appropriate when the flanges are treated as tension or compression members.

C3.2.8 Forï-beams and C-beams, the compression flange should be designedasa column eiemnl in accordance wifh 3.3. For bux-beams, the torsional sfiffness of the whole beam should be cansidered when determining the design strength of the cotnpression flange.

For all built-up beamss the tension flange should be designed as a tension member in accordance with 3.4, Websshou~bedes~nedaspanelsheatheddí~p~~gmsinacco~ancg with 5.2.

3.2.9 Bearing Strength

The bearing strength of a structural element shall satisfy a relationship of the form

Nb $Nnb ...................................................................... (Eq. 3.10)

where

N b = design bearing load Nnb = nominal bearing strength.

= strength reduction factor @ *

The nominal bearing strength, Nnbp, for bearing perpendicular to the grain is

Nnbp = kl k3 fpAp ....................................................................... (Eq. 3.11)

where k7, k3 = modification factors given in section 2,

-

SNZ NZS+3603 93 8583169 0010817 99T =

NZS 3603: 1 993



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SNZ NZS+3603 93 8583369 OOLO8L8 826 =

NZS 3603: 1 993

= =

characteristic bearing stress perpendicular to the grain, bearing area for loading perpendicular to grain.

The nominal bearing strength, N n b / , for bearing parallel to the grain is

!P AP

Nnb/= kl fcAz ...................................................................... (Eq. 3.12)

where kl = modification factor given in section 2 fc = characteristic bearing stress parallel to the grain AI = bearing area for loading parallel to the grain.

The nominal bearing strength, for bearing at an angle of e to the grain is

(Eq. 3.13) Nnbl Nnbp .................................................................. Nnbe = ( N~~ sin2 e + Nnbp cos2 e

C3.2.9 A gtaphical representation of equation 3.13 (Hankinson's formula) is given in figure 4.5.

3.3 Column design

3.3.1 General In thecalculationof strengthforacolumn, due regardshall be paid tothecolumn's effective length and lateral stability. Allowance shall be made for eccentricity of applied loads. See also 3.5 for combined bending and axial loading and Appendix B for the design of lateral and torsional restraints.

3.3.2 Effective lengths The effective length of a column shall be taken as the actual length multiplied by the value of klo corresponding to the condition of end restraint as shown in figure 3.5.

3.3.3 Slenderness coefficient for lateral buckling

3.3.3.1 The slenderness coefficient for lateral buckling shall be as given in 3.3.3.2 or as defined in Appendix D (which gives the general case and certain specific cases) and shall not exceed 85 forcolumns loaded by wind or earthquake loadsonlyor50forall othercolumns. Theslenderness coefficient shall be used to obtain k~ as described in 2.10.

3.3.3.2 For a solid column of rectangular cross section the slenderness coefficients, S2 and % may be taken as:

s, =7 kl oL or Lax d - whichever is the lesser

where klo is as shown in figure 3.5 and

whichever is the lesser

... ....................................... (Eq. 3.14)

.......................... ................ (Eq. 3.15)

provided that if one edge of the column is continuously restrained against lateral displacement & may be taken as

3.5d b

S, =- ....................................................................... (Eq. 3.16)



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NZS 3603: 1993

Condition of end iestiafnt Restrained in position and direction at both ends

Each end held in position and substantially restrained against rotatior (e.0. by two bolts)

One end fixed in position and direction and the other restrained In position only

Restrained in position only at both ends

Restrained in position and direction at one end and at the other partially restrained in direction but not in position

Restrained in position and direction at one end but not res trained in either position or direction at the other end

bflectfon shaps I f member

4 -r-

1 t t J-

*

t

I

1.7

0.75

3,85

I. o

1.5

2.0

Figure 3.5 - Effective length factor, &io



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SNZ NZS*3603 93 = 8583369 O030820 484 NZS 3603:1993

3.3.4 Design The compressive strength of an unnotched column shall satisfy:

cl W n c x and

N>< W n c y ........................................................................................ (Eq. 3.17)

where

N> = design compressive axial load # = strength reduction factor Nncx nominal strength of the member in compression for buckling about the member's

x-x axis Nncv nominal strength of the member in compression for buckling about the member's

Y-Y axis

=

=

The nominal strength for buckling about the member's X-X axis shall be taken as

....................................................................................... (Eq. 3.18) Nncx = kí k f c A

where

kl k8 = stability factor derived using S2 fC = characteristic compressive stress A = cross-sectional area of column

= modification factor for load duration given in section 2

and, for buckling about the member's Y-Y axis

....................................................................................... (Eq. 3.19) Nncy = kí k f c A

where

k8 = stability factor derived using S3

3.3.5 Columns with notches shall be subjected to special study.

3.4 Tension member design

3.4.1 For a member loaded in axial tension only there shall be no limitation on the slenderness coefficient.

3.4.2 Lap joints in tension members shall be avoided in general but if they are used then due allowance shall be made for the resulting bending moment and lateral deflection.

The tensile strength of an unnotched member shall satisfy

(Eq. 3.20) N;< W n t ........................................................................................

where @

Nnt

= strength reduction factor = design tensile axial load = nominal strength of the member in tension.

Ni



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~

SNZ N Z S x 3 6 0 3 9 3 8583169 OOL082L 310

NZS 3603: 1 993

The nominal strength of the member in tension shall be taken as

Nn, = k&f,A ...................................................................... (Eq. 3.21)

where

k7,k4 = the modification factors given in section 2 4 = characteristic tension stress A = cross-sectional area of tension member.

3.4.3 Tension members with notches shall be subjected to special study.

3.5 Combined bending and compression

3.5.1 For combined axial compression and bending in the weak direction (about the Y-Y axis) a column shall be proportioned such that:

[ ML) +Mny + [ A) 4Nncy 51.0 ........................................................................ (Eq. 3.22)

where

M i = design moment about the member's Y-Y axis N i = design axial compression load Mny = nominal bending strength as given in 3.2.4 Nncy = nominal compressive strength as given in 3.3.4

For combined axial compression and bending in the strong direction (about the X-X axis), the column shall be proportioned such that:

and

... ................................................................... (Eq. 3.23)

...................................................................... (Eq. 3.24)

where

M i = design moment about the X-X axis N i = design axial compression load Mnx = nominal bending strength as given in 3.2.4 Nncx = nominal compressive strength as given in 3.3.4

For members subjected to axial compression and bending about both axes, each direction shall be considered separately.



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SNZ NZSx3b03 93 85833b9 0030822 257

NZS 3603:1993 ~~ ~~~ ~ ~ ~

~~

3.6 Combined bending and tension A member subjected to combined bending stress and axial tension shall be proportioned such that:

....................................................................... Eq. 3.25)

where

M* = design moment N; = design axial tension load Mn = nominal bending strength, as given in 3.2.4,

Nnt = nominal strength of member in tension, as given in 3.4.2.

40



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~~~~~ ~ ~

SNZ NZS*3b03 93 85831b9 0030823 193

NZS 3603:1993

4 JOINTS

4.1 General

4.1.1 For the purpose of joint design, timber species shall be assigned to the appropriate group as shown in table 4.1.

c4.1. I Design data have been given only for nails, screws, bolts and coach screws. It is not practWje io include design data for all mechanical fasteners - reference should be made to appropriate publications for this information. Note that the derivation of working loads should comply with the requirements of 4.6 and care is required in adapting data from overseas publications (see AS 1720 and Appendk A).

Table 4.1 - Classification of timber species for joint design

I .

Species Nails and screws in lateral loading

Group for: I I

Radiata pine

Rimu

Douglas fir Larch

Silver beech Red beech Hard beech J4

I

Nails in

drawal With-

Screws in withdrawal

Bolts and coach screws

I J4

4.1.2 Design data for nails, screws, bolts, and coach screws are given in 4.2, 4.3, 4.4, and 4.5 respectively; 4.6 applies to all other fasteners, including variants (for example, so-called "improved nails") of the fasteners covered by 4.2,4.3, and 4.4.

c4.1.2 The values are based on tests conducted in clear timber. Clear timber is not essential for effïcient Jòints but if defects are present in a joint zone, fabricators and inspectors should consider the effect of the local grain direction on joint strength. For example a spike knot surrounding a bok loadedperpendicular to the nominalgrain direction could acfually increase joint strength, whereas a large face knot under a toothed plate connector could, by introducing an area of effective end-grain, substantially weaken the joint.

4.1.3 The deformation of mechanically fastened joints shall be determined in accordance with 4.2.2.3 for nails and Appendix E for other fasteners.

4.1.4 Joints shall be detailed to minimize tension perpendicular to the grain and locaiised shear. in multiple member joints the effect of shear induced by each member shall be checked.



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SNZ N Z S * 3 6 0 3 93 8583369 0030824 02T

NZS 3603: 1 993

4.2 Nails

4.2.1 General

C4.2.f Nail heads Thin p l y d and particle board material require nails with relatively large flat heads. Nails with brad, ptf or other small heads shoukinot be used. Large flat headed nails are no€ required in pints with thick plates because nail head rotational restraint is nof important,

4.2.1.1 Clause 4.2 applies to joints with plain or galvanized steel wire nails irrespective of whether the loads (not the nails) are parallel, perpendicular, or at an angle to the grain.

c42.1. 1 The characteristic badsin table 4.3applyspecifi~lly to nails driven into side grainkxiloaded pependkular to their length, but allowance for slant-driven nails is made in 4.2.1,2, and for nails in end-grain in 4.2,2.2(c). Withdrawal loads are covered by 4.2.3.

4.2.1.2 Nails loaded laterally shall not be slantdriven except in joints where no reversal of stress can occur in service and the direction of the slant is such that the joint will tend to tighten under load, in which case table 4.3 applies.

4.2.1.3 Significant splitting shall be avoided.

C4.2.1.3 The design strengths are based on the assumption that splìîting of the timber does not occur to any significant extent.

Signifikant splitting is splitting of P severity that clearly would cause a large reduction in the shear strength of the timber in the vicinity of the joint, making rigEd fixing (in resped of setvice loading) unlikely and offering a very limited resistance to any tensile force applied to the joint.

In timber that tends to split signifkantly when nailed withoutpreboring, preboredhoks having a diameter 80 % of that of the nail shoukl be used.

It is notpssible to give precise guidance on identifying timber that is likeíy to split signikantly when nailed near an end. Relevant factors include species, density, straightness of grain, moisture content, spacing of nails, size of nails, shape of point, and manner of driving. In the absence of directly applicable experience, often a trial with the proposed nailing detail is the only reliable gude.

Splitting has occurred in radiata pine of higher than normal densrty when nailed with greater spacing along the grain than shown in table 4.2. splitting can also be marked in green timber when machhe nailing is used. specrál care should be taken during construction to ensure that spliìting döes not occur.



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~~ ~

SNZ NZSa3b03 93 9 8583169 0030825 Tbb

NZS 3603: 1 993

'Minimum spacing of nails - No preboring AI1 timber except Radiata pine

'Minimum spacing of nails - No preboring Radiata pine only

Minimum spacing of nails and screws - Prebored to O . M a All timber

&da f tension] 5da (compression) 5da

Direction of load (refer Eq.4.10)

rT1

Minimum spacing of bolts - Loaded parallel to grain All timber la is given in 4.4.1.3 r a i l

Loaded

Directton of load (refer Eq.4.11)

Minimum spacing of bolts - Loaded perpendicular to grain All timber la is given in 4.4.1.3 ( b ) )

Figure 4.1 - Positioning of fasteners



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~ ~~

SNZ NZSx3b03 93 8583Lbî 00L082b 9T2

Distance Hole not prebored (nails only)

NZS 3603:1993

Hole prebored to 0.8 da or as given by 4.3.7.2 for screws

4.2.1.4 Edge and end distances and spacing of nails in a nailed joint shall be not less than is given in table 4.2 (see also figure 4.1).

From end of member

From edge of member

Between nails along grain

Between nails across grain

20 da 10 da may be reduced to 12 da for radiata pine

5 da 5 da

20 da 10 da may be reduced to 1 O da for radiata pine

10 da 3 da may be reduced to 5 da for radiata pine

4.2.2 Lateral loads

C4.2.2 Seismic design The average ultimate strength of nailed connections in single shear is approximately 1.6 times the chamcteristicstrength given in table 4.3. Hence for capacity design, an overstrength factor of 1 .H$ = 2. O should be used.

4.2.2.1 The characteristic strength for nailed joints in solid timber shall be as in table 4.3.

The characteristic strength for flat head nails through plywood or particle board shall be:

(a) on J5 timber, the value given in table 4.3 for J5 timbers

(b) on other timbers, 1.1 times the value given in table 4.3 for J5 timber.

c4.2.2.1 The characteristic strengths for nails in table 4.3 have been deriveâ by apPying a soft conversion muit@lier of 2.95 to the basic working loads used in previous versions of the Standard. The resulting values in table 4.3 generally coincide with the average strength of nails at a slip of O.# mm, or 0.625 times the average strength af a slip of 2.5 mm.

4.2.2.2 Laterally loaded nailed joints shall be so proportioned to satisfy

S*I $Q,, ......................................................................... (Eq. 4.1)

where

$ = strength reduction factor



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~

SNZ NZSa3603 93 = 8583369 0010827 839 =

NZS 3603:1993

Qn s'

= = = =

nominal strength of a joint appropriate to mode of loading design load effects on joint produced by strength limit state loads #' for direct loads with no moment M* for in-plane moments with no direct loads.

For directly loaded joints, the nominal strength shall be taken as

O, = nkQk ........................................................................................... (Eq. 4.2)

and for joints subjected to in-plane moments the nominal strength can be taken as

provided that direct effects from shear and axial loads are insignificant compared with bending effects,

where

n = number of fasteners Qk = characteristic strength as given in 4.2.2.1 ri r,, = the maximum value of r i k = product of modification factors listed below:

= the distance of the i th nail to the centroid of the nail group

(a) Green timber (see table 2.1) 0.85

(b) Duration of loading Factor kl as given by 2.7

(c) Nails in end grain 0.67

(d) Nails in double shear 2.0

(e) Steel side plate < 3.0 mm thickness 1.25 1.5 1.4

Steel side plate 2 3.0 mm thickness Plywood or particle board with flat head nails

(f) Nail length and timber thickness. For the characteristic strengths given in table 4.3 to be applicable, timber thicknesses and nail length (figure 4.2) shall be such that:

(i) Two-member joints (nails in single shear) -

thickness of first member, tl > 10 da in solid timber tl > 1.5 da in plywood or particle board

depth of penetration of nail into second member, p > 1 O da

For lesser values of tl and p, the characteristic strength shall be reduced in proportion to the decrease in tl or p, and the nails shall be considered as non-load-bearing if fi or p is less than 5 da in solid timber.

(i) Three-member joints (nails in double shear): thickness of central member fi > 1 O da , thickness of outer member to > 7.5 da, depth of penetration of nail into outer member, p > 7.5 da.



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~ ~~

SNZ NZS*3603 93 m 8583369 0030828 775 m

NZS 3603: 1 993

For lesservalues of tl , 4 and p, thecharacteristic strength shall be reduced in proportion to the decrease in t l , 4 and p, and the nails shall be regarded as being in single shear if p is less than 5 da.

(g) Number of nails. For connections containing 50 or more nails the design strength shall be increased by 1.3. For fewer nails, the factor shall be obtained by linear interpolation to value of 1 .O for four nails.

c4.2.2.2 The lateral characteristic strengths of table 4.3 may be used for "improved" nails of common steel having twisted, annulady grooved, or helically grooved shanks. However, although such "inymved"nai1s have a greaterchmphg action andgive greater ultimate strength, the joint may not be as stiff as with plain-shanked nails. Preboring may be necessary to enable improved nails to be driven into timbers other than those of groups J5 and J4.

(e) Nails driven through close holes in steel side plates are stiffer than nailed wood to wood connections. This increase is more pronounced for thick side plates which provide better rotational resistance to the head of the nail.

(g) The effect of clause (g) is to produce design nail strengths that are close to the average rather than the lower five percentile value.

Table 4.3 - Characteristic strengths (N) for one plain steel wire nail in single shear in side grain in dry timber

f Nail shankdiameter (mm)

2.0 2.24 2.50 2.80 2.87 3.15 3.33 3.56 3.75 4.00 4.50 5.00 5.30 6.00

268 331 407 504 526 631 ô95 790 868 990 1240 15101690 2130 391 476 577 703 733 863 951 1060 1165 1310 1610 19302140 2660 550 671 812 990 1030 1220 1345 1500 1650 1840 2270 27203010 3740 ô80 824 993 1200 1250 1470 1MO 1800 1980 2200 2690 32103640 4370 743 908 1100 1350 1410 1660 1830 2060 2260 2540 3130 377'04190 5220

(a) Two-member joint (b) Three-member joint

Figure 4.2 - Timber thickness and nail length

4.2.2.3 Deformations In the absence of specific test data, slip in nailed joints may be determined from the following:

(a) A load equal to 1.25 times the nominal short term strength of a single nail gives an average slip of 2.5 mm.



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~~

SNZ NZSx3b03 93 W 8583169 0030829 b o l =

Timber group

NZS 3603: 1 993

Nail shank diameter (mm)

2.0 2.24 2.50 2.80 3.15 3.55 4.00 4.50 5.00 5.30 6.00 6.30

(b) From O to 0.5 mm slip, the slip can be calculated from

J5 J4 J3

J1 &J2

k37 (O. 8)P2 6= Q"*

4.2 4.7 5.2 5.8 6.5 7.3 8.3 9.3 10.3 10.9 12.3 12.9 5.5 6.2 6.8 7.7 8.6 9.7 11.0 12.4 13.8 14.6 16.6 17.4

10.6 11.9 13.3 14.9 16.7 18.9 21.3 23.9 26.6 28.1 32.0 33.6 15.3 17.1 24.5 21.4 24.1 27.1 30.4 34.3 38.1 40.6 45.7 48.0

........................................................................ (Eq. 4.4)

where

k37 = is given in table E l in Appendix E P = applied nail load C?, = nominal strength for a single nail with short term loading (k7 = 1).

(c) From 0.5 mm to 2.5 mm slip, interpolate linearly between (a) and (b).

(d) Above 2.5 mm slip, the load may increase 20 % to 40 % to give maximum load at a slip between 6 mm and 10 mm.

4.2.3 Withdra Wal loads

4.2.3.1 The strength limit state withdrawal load on a nail driven into the side grain of timber shall not exceed the appropriate characteristic value given in table 4.4 multiplied by the depth of penetration and the strength reduction factor. The withdrawal strength does not depend on the duration of load or on whether the timber is green or dry.

4.2.3.2 No load in withdrawal shall be carried by a nail driven into end grain, except fortwo or more nails into the end grain of pinus radiata where the values for timber group J4 as given by table 4.4 for nails in side grain may be applied.

C4.23 If practicable, the design should be such that there is no load component parallel to the axis of the nail tending to withdraw it. Resistance to withdrawal may be improved by the use of clinching, double skew-nailing, rough gaivanised nails, or improved nails. Withdra Wal loads can often be eliminated by using nailed steel side plates.

rable 4.4 - Characteristic withdrawal strength per millimetre of nail penetration (N/mm) for one plain steel wire nail in side grain

4.3 Screws

4.3.1 General

4.3.1.1 Clause 4.3 applies to joints made with wood screws irrespective of whether the loads (not the screws) are parallel, perpendicular, or at an angle to the grain.



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SNZ NZSs3603 93 m 8583169 0010830 323 m

NZS 3603: 1 993

C4.3.1.1 The characteristk strengths in table 4.5 applyspecíf~lly to screws screwedinto sMle grain and loaded perpendicular to their length, but allowance for screws in end grain is made in 4.3.2(c).

4.3.1.2 The correct sizes of lead holes shall be bored for all screws except self drilling screws. The diameter of the hole for the shank shall be equal to the diameter of the shank, and the lead hole for the threaded portion of the screw shall not exceed the root diameter of the screw.

4.3.1.3 Edge and end distances and spacing of screws in a screwed joint shall be not less than is given in table 4.2 and figure 4.1.

4.3.2 Lateral loads Laterally loaded screwed joints should be so proportioned to satisfy

S* 5 @Qn ........................................................................................... (Eq. 4.5)

where

9 = strength reduction factor Qn = nominal strength of joint S* =

= =

design load effects on joint produced by strength limit state loads N* for direct loads with no moment M* for in-plane moments with no direct loads.

For directty loaded joints, the nominal strength shall be taken as

........................................................................................... Qn = nkQk (Eq. 4.6)

and for joints subjected to in-plane moments the nominal bending strength can be taken as

i=n Qn = - Q r c r i 2 ........................................................................................... (Eq. 4.7)

rmax i=l

provided that direct effects from shear and axial loads are insignificant compared with bending effects,

where

n = number of fasteners Qk = characteristic strength as given in table 4.5 ri rma = the maximum value of r i k = product of modification factors listed below:

= the distance of the i th screw to the centroid of the screw group


(b) Duration of loading Factor kl as given by 2.7

(c) Screws in end grain 0.67

(d) Steel side plates 1.25 where screws are driven through close-fitting holes in steel side plates that are of adequate strength to transfer the load.



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SNZ NZSx3603 93 = 8583169 001083L 26T

Timber group

NZS 3603: 1 993

Minimum screw shank diameter (mm)

2.74 3.10 3.45 3.81 4.17 4.52 4.88 5.59 6.30

Screw gauge number

(e) Screw penetration The characteristic lateral strengths given in table 4.5 are in accordance with the assumption that the depth of penetration of the screw into the member receiving the point is not less than seven times the shank diameter (7 da). For depths of penetration less than this value the characteristic strength shall be reduced in proportion to the reduction in penetration but the minimum acceptable penetration depth shall be four times the shank diameter (4 da).

700 960

1356 1635 1846

Table 4.5 - Characteristic strength (N) for one steel wood screw in single shear in side grain in dry timber

854 1155 1634 1964 2235

9

1429 1855 261 5 3098 3606

10

1652 2118 2985 3526 41 33 -

3786 4439 5429 5276 6503

NOTE - Maximum screw shank diameter = above mentioned shank diameter + 0.13 mm.

4.3.3 Withdrawal loads

Screwed joints subjected to withdrawal loads shall be proportioned to satisfy

........................................................................................................ Na I t#Qn (Eq. 4.8)

where

&ìn

N" Qn = nominal strength.

=

=

design strength not exceeding the appropriate value given in table 4.6 times the number of screws in the joint design load effects on joint produced by strength limit state loads

The nominal strength is given by

Qn = n@Qk ...................................................................................................... (Eq. 4.9)

where

n = number of screws in joint Qk = characteristic load given in table 4.6 P = penetration length of screw k = product of the modification factors listed below.


(b) Duration of loading Factor k1 as given by 2.7

(c) Screw in end grain 0.67

49



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NZS 3603: 1 993

Table 4.6 - Maximum design withdrawal strength for one steel screw in dry timber

Screw shank dia. (mm) 2.74 3.10 3.45 3.81 4.17 4.52

Screw gauge No. 4 5 6 7 8 9

Load (N) 1030 1320 1630 1980 2380 2790

4.88 5.59 6.30

10 12 14

3270 4280 5440

Table 4.7 - Characteristic withdrawal strength per millimetre of screw thread penetration (N/mm) for wood screw insetted

at right angles to the grain of dry timber

2.74 I 3.10 I 3.45 I 3.81 I 4.17 4.52 I 4.88 I 5.59

J4 & J5 J3 J2 J1

6.30

4 5 6 7 8

34.7 38.1 43.5 47.9 52.6 53.6 61.0 67.7 75.5 82.6 77.5 88.3 98.7 110 121

112 130 149 168 188

4.4 Bolts

9 10 12 14

57.0 61.7 70.8 79.5 89.6 97.1 112 126

132 143 164 186 207 228 270 310

4.4.1 General

4.4.1.1 The diameter of the hole for a bolt shall be not less than the bolt diameter and shall not exceed it by more than 10 %.

4.4.1.2 In timber-to-timber bolted joints where the bolt is not in tension, every bolt shall be provided with a washer at each end of size not less than:

20 mm x 20 mrn x 1.5 mm for bolts not exceeding 8 mrn diameter

35 mm x 35 mm x 3 mm for bolts not exceeding 12 mm diameter

50 mm x 50 rnrn x 4 mm for bolts not exceeding 20 mm diameter

65 mrn x 65 rnrn x 5 mrn for bolts exceeding 20 mm diameter

provided that if round washers are used they shall be of a thickness and area not less than those specified above for the equivalent square washer.

For joints with bolts in tension, the major dimensions above shall be increased by a factor of 1.3.

50



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SNZ NZS*3603 93 85633b9 0030833 O32

NZS 3603:1993

4.4.1.3 Edge and end distances and spacing of bolts in a bolted joint shall be not less than:

(a) Load parallel to grain:

As shown in figure 4.1 with:

(Eq. 4.10) ................................................................................ r -1

but not less than 2.5 da

where

n =total number of bolts in joint r = number of rows of fasteners across the grain.

(b) Load perpendicular to grain:

As shown in figure 4.1 with:

a = 0.625 b + 1.25 da

but not less than 2.5 daor greater than 5 da

where

b = thickness of member with load perpendicular to grain.

............................................................................... (Eq. 4.1 1)

c4.4.1.3 It Ìs not practicable to provide general rules for the spacing of bolts to cover all possible directions of appliedload to the grain. The requirementsof 4.4. I. 3(a) and (b) shouldtherefore be used as a guide for boltedjoints with loads actingat an angle other than perpendicuiaror parallel to the grain. Stress concentratlóns should be minimized, aWYo obtain uniform stress in main membersanda uniform distribution of bad to allbolts, thegrsivityaxisof the members is required to pass through the centre of resistance of the bolt groups.

4.4.1.4 For eccentric joints, the combination of primary and secondary stresses shall be checked to ensure that no member or fastener is stressed excessively, and

V* I @kl k4ksfSbds ....................................................................... (Eq. 4.12)

where

V* = k7 to k5 =

= capacity reduction factor = characteristic shear stress

4 fS

=

design shear force produced by strength limit state design loads modification factors of section 2

b = thickness of timber member dS depth of member less the distance from the unloaded edge to the centre of the bolt

(see figure 4.3)

C4.4.1.4 An eccentric joint is one in which it has been found impracticable to ensure that all the members meeting at the joint are arranged symmetrically with their centrelines intersecting on a common axis that is also the axis of resistance of the bolt orgroup of bolts. fccentrìcity results in bending moments causing secondarystresses, In the caseof splìtrings, nailplates and other fasteners having substantialarea, the distance ds should be measured to the edge of the fastener furthest from the Eoadeá edge.



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SNZ N Z S x 3 6 0 3 93 8583169 001083Y T79

Timber group J5 J4 J3 J2

kll 2.0 2.0 2.0 1.75

NZS 3603: 1 993

J1

1.65

Unloaded edge

fcj (MPa) 36.4 45.2 57.6 72.5 ~

Figure 4.3 - Eccentric joints

4.4.2 Characteristic strengths

(a) Two member single shear joint:

(i) For parallel to the grain loading in dry timber, the characteristic strength, Qklfor a bolt in single shear shall be the lesser of:

where

kl1 = factor given in table 4.8 fcj = bolt bearing stress as given by table 4.8 da = bolt diameter in mm be = effective timber thickness in mm as given by table 4.9

Characteristic strengths computed in accordance with this sub-clause are given in table 4.1 O and figure 4.4.



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SNZ NZSr3603 93 = 8583167 0010835 905

NZS 3603: 1 993

Table 4.9 - Characteristic strength for a single bolt in dry timber loaded parallel to the grain

Type of joint

1. Two member

2. Three member

3. Multiple member

I A I iL

.c I 1”; O

4. Alternative steel and timber members

Effective timber thickness

(be)

Smaller of 2h and 2b2

Smaller of 261 and i~

(i) Between A and B Smaller of b1 and b2

(i) Between B and C Smaller of 61 and

(iii) etc.

_ _ _ _ _ _ _ _ ~

As for types 1,2 or 3 except that be is based on thickness of timber members only

System characteristic strength

os&/

Qkl

2 Qkl

(i) Qkl (¡i) Qkl (iii) etc.

Total characteristic load = sum of characteristic loads

1.25 x value calculated for joint types 1,2, or 3



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SNZ NZS+3603 93 ô583169 O010836 841

NZS 3603:1993

O 20 40 60 80 100

imm //

120 14 O 160 18 o Effective thickness (mml

(Twice thickness of thinner member)

Figure 4.4 - Characteristic strength for a boit in a two-member joint in dry radiata pine or Douglas fir

54



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~ ~~~

SNZ N Z S * 3 b 0 3 9 3 = 8583167 0010837 7 8 8 W

NZS 3603: 1 993

Table 4.10 - Characteristic strength, ûskl(kN) for a single bolt in a two-member joint

Effective timber thickness [be)

[mm)

15

19

35

45

65

90

130

Boit shank dia.

(mm)

8 10 12 16 20 24

8 10 12 16 20 24

10 12 16 20 24 30

12 16 20 24 30

12 16 20 24 30

12 16 20 24 30

12 16 20 24 30

in dry timber loaded parallel to the grain

Timber group

J5 54 53 52 J1

2.16 2.70 3.25 4.33 5.41 6.49

2.74 3.43 4.1 1 5.48 6.85 8.22

6.31 7.57 10.1 12.6 15.1 18.9

9.74 13.0 16.2 19.5 24.3

10.4 18.5 23.4 28.1 35.2

10.4 18.5 28.8 38.9 48.7

10.4 18.5 28.8 41.5 64.9

2.18 2.73 3.28 4.37 5.46 6.55

2.77 3.46 4.15 5.53 6.92 8.30

6.37 7.64 10.2 12.7 15.3 19.1

9.83 13.1 16.4 19.7 24.6

10.5 18.6 23.7 28.4 35.5

10.5 18.6 29.1 39.3 49.1

10.5 18.6 29.1 41.9 65.5

2.71 3.39 4.06 5.42 6.77 8.13

3.43 4.29 5.15 6.86 8.58 10.3

7.90 9.48 12.6 15.8 19.0 23.7

12.2 16.3 20.3 24.4 30.5

13.0 23.1 29.4 35.2 44.0

13.0 23.1 36.1 48.8 61 .O

13.0 23.1 36.1 52.0 81.3

3.46 4.32 5.19 6.92 8.64 10.4

4.38 5.47 6.57 8.76 10.9 13.1

10.1 12.1 16.1 20.2 24.2 30.3

14.5 20.7 25.9 31.1 38.9

14.5 25.8 37.5 44.9 56.2

14.5 25.8 40.3 58.1 77.8

14.5 25.8 40.3 58.1 90.8

4.35 5.43 6.52 8.69 10.9 13.0

5.51 6.88 8.26 11.0 13.8 16.5

12.0 15.2 20.3 25.4 30.4 38.0

17.2 26.1 32.6 39.1 48.9

17.2 30.6 47.1 56.5 70.6

17.2 30.6 47.8 68.9 97.8

17.2 30.6 47.8 68.9 108

55



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~

SNZ NZSx3b03 93 = 8583Lb9 OOL0838 bL 4

Timber group J5 54 53 J2

kl1 14.9 17.6 15.1 12.6

fpj ( M W 12.9 13.6 14.5 22.7

NZS 3603: 1 993

J1

10.1

28.9

(i) For perpendicular to the grain loading in dry timber the characteristic strength, Qkpfor a bolt in single shear shall be the lesser of:

where

k l1 = factor given in table 4.1 1 bi = stress as given by table 4.1 1 da = bolt diameter in rnm be = effective timber thickness in mm as given by table 4.12.

Characteristic strength 4.12 and 4.13 and figure 4.5.

computed in accordance with this sub-clause are given in tables

Table 4.12 - Characteristic strength for a single bolt in dry timber loaded mrmndicular to the arain

Type of joint

Pl 1. Two member

2. Three member

3. Multiple member

4. Alternative steel and timber members

w

Effective timber thickness

be

2b, but not exceeding mice the thickness of the side member

~ ~~ ~ ~

Smaller of 2b1 and 9 as appropriate for members loaded perpendicular to the grain

(i) Between A and B Smaller of bl and 4

(i¡) Between B and C Smaller of 9 and

(iii) Between C and D Smaller of b3 and b4

(iv) etc.

As for types 1,2 or 3

System characteristic strength

QskP

(i) Qkp

(iii) (N) etc.

Total characteristic load = sum of characteristic loads

(ii) Qkp

No increase over value calculated for joint types 1,2,or3



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SNZ NZSx3603 93 8583169 0020839 550

12 16 20 24 30 36

12 16 20 24 30 36

12 16 20 24 30 36

NZS 3603: 1 993

3.48 3.69 3.90 6.1 3 7.80 4.65 4.91 5.20 8.18 10.4 5.81 6.14 6.51 10.2 13.0 6.97 7.37 7.81 12.3 15.6 8.71 9.21 9.76 15.3 19.5 10.5 11.1 11.7 18.4 23.4

5.03 5.32 5.64 8.86 11.3 6.71 7.10 7.52 11.8 15.0 8.39 8.87 9.40 14.8 18.8 10.1 10.6 11.3 17.7 22.5 12.6 13.3 14.1 22.1 28.2 15.1 16.0 16.9 26.6 33.8

6.97 7.37 7.81 11.9 12.1 9.29 9.83 10.4 16.4 18.7 11.6 12.3 13.0 20.4 26.0 13.9 14.7 15.6 24.5 31.2 17.4 18.5 19.5 30.7 39.0 20.9 22.1 23.4 36.8 46.8

Table 4.13 - Characteristic strength, Ci+ (kN) for a single bolt in a two-member joint in dry timber loaded perpendicular to grain

Effective timber thickness (be)

(mm)

15

19

35

45

65

90

130

180

Boit shank dia. Timber group

8 10 12 16 20 24

0.774 0.81 9 0.867 1.36 1.73 0.968 1 .o2 1 .O8 1.70 2.17 1.16 1.23 1.30 2.04 2.60 1.55 1.64 1.73 2.72 3.47 1.93 2.05 2.1 7 3.41 4.33 2.32 2.46 2.60 4.09 5.20

~

8 10 12 16 20 24

0.981 1 .O4 1.10 1.73 2.1 9 1.23 1.30 1.37 2.1 6 2.74 1.47 1.56 1.65 2.59 3.29 1.96 2.07 2.20 3.45 4.39 2.45 2.59 2.75 4.32 5.49 2.94 3.1 1 3.30 5.1 8 6.58

10 12 16 20 24 30

2.26 2.39 2.53 3.97 5.05 2.71 2.87 3.04 4.77 6.06 3.61 3.82 4.05 6.36 8.09 4.52 4.78 5.06 7.95 10.1 5.42 5.73 6.07 9.54 12.1 6.78 7.1 7 7.59 11.9 15.2

12 16 20 24 30

7.99 9.99 9.07 11.9 12.1 12.3 14.2 14.0 18.3 18.7 16.8 17.7 18.8 25.6 26.1 20.1 21.3 22.6 33.6 34.3 25.2 26.6 28.2 44.3 47.9

12 16 20 24 30

7.99 9.99 9.07 11.9 12.1 12.3 15.4 14.0 18.3 18.7 17.2 21.5 19.5 25.6 26.1 22.6 28.2 25.7 33.6 34.3 31.6 36.9 35.9 47.0 47.9



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NZS 3603:1993

(b) Bolted joint systems

The characteristic strength, Qsk, for a laterally loaded single bolt in a bolted system, shall be derived as follows:

(i) For systems loaded parallel to the grain:

................................................................... (Eq. 4.1 3) Qsk = QsM

where Qsk/ is the system characteristic strength given in table 4.9.

(i¡) For systems loaded perpendicular to the grain:

................................................................... (Eq. 4.14) Qsk = ‘skp

where Os@ is the system Characteristic strength given in table 4.12.

(iii) For systems loaded at an angle, 8, to the grain:

(Eq. 4.15) QsklQskp ................................................................... QsM sin2 8 + Qsrcp cos2 8 Osk =

where Qsk/and Qskp are system characteristic strengths given in tables 4.9 and 4.12.

c4.4.2 A graphical representation of equation 4.15 (Hankinson’s formula) is given in figure 4.5.

4.4.3 Strength of bolted joints

4.4.3.1

The strength of laterally loaded bolted joints, for the strength limit state shall satisfy

N* I $Qn ....................................................................... (Eq. 4.1 6)

where

= strength reduction factor = N

Qn = nominal joint strength. design load effects on joint produced by strength limit state loads

The nominal joint strength shall be taken as

a n = nklkl2kl3Qsk ....................................................................... (Eq. 4.1 7)

where

n = number of bolts in joint kl = load duration factor of section 2 k12 k13 Qsk = system characteristic strength as given in 4.4.2(b).

= =

modification factor for green timber as given in table 4.14 modification factor for multiple number of fasteners as given in 4.4.3.2



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~

SNZ NZS*3603 9 3 9 8583169 O O L O 8 4 1 109 9

NZS 3603:1993

Example: Given a 16 mm boiî in single shear through J5 members of 90 mm effective timber thickness with the resuitant load inclined at 60' to the grain. To find Qsk connect QsH = 18.5kN (tables 4.9 and 4.10)to Q,,=9.29 kN (tables4.12and4.13). At the intersection with the 60" line, construct a line parallel to the grid to the vertical or horizontal axis to read off O,, = 10.6 kN.

O 5 10 15 20

fp Or Qskp

Figure 4.5 - Graph of Hankinson formula for stresses and loads



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SNZ NZS*3b03 93 9 8583169 OOL0842 045 9

NZS 3603: 1 993

4.4.3.2 (a) In dry timber (see table 2.1): The modification factor k13 is as given by table 4.15.

(b) In green timber (see table 2.1):

(1) Where the joint details impose no restraint on the shrinkage of the joint: The modification factor, k13, is as given by table 4.15.

(2) Where the joint details impose restraint on the shrinkage of the joint: k13 = 0.5 shall be used provided that where deformation is of no significance k13 as given by table 4.16 shall be used.

C4.4.3.2(b) Examples of joint details that impose no restraint on the shrinkage of the joint are where the bol& are in a single rowparallel to the grain or in mu/t@le rows loadedparallel to the grain with a separate splice platt? for each row.

Table 4.14 - Factor, 4 2 for bolt and coach screw joints in green timber

I Timber group J5 J4 J3 J2 J1

k12 0.7 0.75 0.85 0.85 0.85

Table 4.15 - Factor, k13 for the design of multiple bolt and multiple-coach-screw joints

Total number of 4 5 10 16 bolts or coach or fewer or more screws in joint

I k13 1 .o0 0.95 0.80 0.62

4.4.3.3 If the load acts at an angle to the bolt axis the component of load perpendicular to the bolt axis shall satisfy the requirements of 4.4.3.1, and the load component parallel to the bolt axis shall satisfy

N* I @Cì" ....................................................................... (Eq. 4.18)

where

= strength reduction factor = N*

Q n = nominal joint strength. design load effects on joint parallel to the axis of bolt


....................................................................... (Eq. 4.19) Qn = f p j b

where

= =

as given in table 4.1 1, area of washer, not less than required by 4.4.1.2.

%i A W



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SNZ NZS*3b03 93 M 8583369 0030843 T83

NZS 3603: 1 993

4.5 Coach screws

4.5.1 General

4.5.1.1 The diameter of the hole forthe shank of a coach screw shall be not less than the shankdiameter and shall not exceed it by more than 1.5 mm. The diameter of the hole for the threaded portion shall not exceed the root diameter of the screw, and its depth shall be at least two diameters greater than the intended depth to which the screw is to be driven.

4.5.1.2 Coach screws shall not be hammered into place but turned with a wrench.

4.5.2 Lateral loads The strength of laterally loaded coach-screwed joints shall satisfy

N* I @Qn ....................................................................... (Eq. 4.20)

where

= strength reduction factor = h

Qn = nominal joint strength. design load effects on joint


Qn = nkí h2kí 3Q.k ....................................................................... (Eq. 4.21)

where

n = number of coach screws in joint k7 = load duration factor of section 2 k12 = modification factor for green timber as given in table 4.14 k73 = modification factor for multiple number of fasteners as given in 4.4.3.2 Qsk = system characteristic strength as given in 4.4.2(b) for a bolted joint with the same

shank diameter as the coach screw k = modification factors as given below

(a) Member thickness: if the thinner member in a two-member joint has a thickness less than three times the shank diameter the nominal lateral load shall be reduced in direct proportion.

(b) Depth of penetration: If the depth of penetration is less than:

(i) 1 O shank diameters in timbers of groups J5 and J4, or

(i¡) 8 shank diameters in timbers of group J3, or

(iii) 7 shank diameters in timbers of groups J2 and J1,

then the nominal strength shall be reduced in direct proportion.

4.5.3 Withdra Wal loads Coach screw joints subjected to withdrawal loads shall satisfy

N* I @Qn ....................................................................... (Eq. 4.22)

61



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~~ ~

SNZ NZS*3603 'i3 m 8583169 0010844 918 m

Timber group

NZS 3603: 1 993

where

Shank diameter (mm) 6 8 10 12 16 20

= strength reduction factor = design load effects on joint

4 N* Qn = nominal joint strength.


Q,, = nkpQk ....................................................................... (Eq. 4.23)

where

n = number of coach screws in joint P = length of penetration of coach screw Qk = characteristic withdrawal strength of table 4.16 k = modification factors listed below.

(a) Green timber (see table 2.1):

(i) 0.7 for timbers of group J5, (i) 0.85 for timbers of groups J4.

(b) Duration of loading: Factor kl as given by 2.7.

(c) Coach screw in end grain ...................... 0.67

Table 4.16 - Characteristic withdrawal strength per millimetre of penetration of thread (N/mm) for a coach screw in dry timber

96 1 07 118 136 152 120 134 147 1 70 189

189 208 242 272 197 229 256 281 325 364

320 350 404 455

r[ii 286 168

248

4.6 Other mechanical fasteners

C4.6 Clause 4.6isapplicable to the manypatented and spechlised wchanicalfasfenings, usually of metal, that have been developed to provide effective structural joints between timber members or between steel and timber. These include "improved" nails, toothed-plate connectors, split-ring connectors, .shear$iare connectors, double-sided round toothed plafes, and other types of fasteners.

4.6.1 General

4.6.1.1 Clause4.6 applies to any mechanical fastener not specifically covered by 4.2 to 4.5 inclusive. For the purposesof this Standard a fastener is defined as a complete unit required in the construction of a sound structural joint.



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S N Z NZSr3603 93 W 8583169 0030845 854 W

NZS 3603: 1 993

4.6.1.2 Each type of fastener shall have characteristic strengths determined according to Appendix A. Where dry or seasoned timber is concerned in relation to this Standard its moisture content shall be not greater than 18 %.

4.6.1.3 Edge and end distances and, where applicable, spacing of fasteners on the same face or on an opposite face of a timber member in a joint shall be not less than those that were used in the derivation of characteristic strengths.

4.6.2 Design strengths

4.6.2.1 General The design strength for a joint made with mechanical fasteners shall be obtained by multiplying the characteristic strength by the appropriate strength reduction factor, Q, and the modification factors given in 4.6.2.2 to 4.6.2.8 as appropriate to the service conditions and provided that the resulting design strength shall not exceed the design strength of any pari of the fastening system.

4.6.2.2 Moisture condition The characteristic strength shall be that appropriate to the service and moisture condition of the timber.

4.6.2.3 Duration of loading Thecharacteristicstrengthshall be multiplied by thefactor, kl asgiven by2.7. Wherethestrength of a joint is determined by the strength of the material of the fastener, the load duration factor shall be that appropriate for the material.

4.6.2.4 Double shear For a fastener capable of acting either in single or double shear, the characteristic strength, if determined by tests in single shear, shall be doubled where the fastener is used in double shear. Conversely, if the characteristic strength was determined by tests in double shear it shall be halved where the fastener is used in single shear.

4.6.2.5 Metal side plates Unless otherwise indicated by tests in accordance with Appendix A an increase of 25 % is permitted where the fastener is used as a jointing medium between timber and steel.

4.6.2.6 Multiple fasteners The total design strength for a joint containing more than one fastener shall be the sum of the design strengths for the several fasteners in the joint multiplied by kl3 as given by 4.4.3.2 as appropriate, unless tests in accordance with Appendix A indicate that other factors are applicable.

4.6.2.7 Angle to grain Where a fastener has different Characteristic strengths in bearing parallel and perpendicular to the grain, the design strength in bearing at an angle 8 (other than O" to 90") to the grain shall be computed from the Hankincon formula as in 4.4.2(b)(iii).

4.6.2.8 Other conditions Increases or decreases to the characteristic strengths shall apply as specified in 4.2 to 4.5 inclusive for fastenings, (such as nails and bolts) most closely related to the particular fastener being used.

4.7 Glued joints

4.7.1 Rigid adhesives The use of rigid adhesives for structural joints shall comply with NZS 3606.



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~~

SNZ NZS*3603 93 8583167 0030846 790 U

NZS 3603: 1 993

4.7.2 Elastomeric adhesives

4.7.2.1 General Elastomeric adhesives shall be considered to contribute to the strength or stiffness of a structure for resisting wind, earthquake, or other loadsof a transitory natureonly; no other short or long term loading shall be assumed to be resisted by an elastomeric adhesive glued joint.

C4.7.2. I Elastomerk adhesives are characterised by moderate resistance to shott-term loads, high creep under sustained loads, and the abiliìy to retain their adhesive properties after large deformations normal to or in the plane of the adherand surface.

4.7.2.2 Fixing of elastomerically glued joints In all elastomerically glued joints adequate mechanical fastenings shall be provided to maintain the adhered surfaces in contact.

4.7.2.3 Strength and stfiness of mechanical fastenings in elastomerkally glued pinis. For short term loads, the mechanical fastener shall be assumed to make no contribution to the strength or stiffness of the joint. For long term loads the elastomeric adhesive will creep and the maximum load shall be that of the mechanical fastener. The stiffness under long term load will depend on the creep properties of the particular elastomeric adhesive. Behaviour should be somewhat stiffer than a purely mechanically fastened joint.

C4.7.2.3 Short term Foads carried by elastomeric beads or daubs are very much higher, and the joints very much stiffer than are provided by normal nailing densities. The adhesive carries a// the load without sufficient slip to mobilise a load in the nail.

4.7.2.4 Strength properties of elastomeric adhesives The strength properties of elastomeric adhesives that are used in design shall be established by tests made on the same formulation of adhesive, specified by brand name andtype, and the same types of mating surfaces as are to be used.

4.7.2.5 Design strength The design shear strength shall be taken as one-third of the mean ultimate shear stress determined by tests, and the shear stiffness used in design shall be taken as the mean of the test stiffnesses at that design shear strength.

4.7.2.6 Compatibility The formulation of elastomeric adhesive shall be compatible to the timber adherand surface and the test results obtained shall be applied only to the formulation of elastomeric adhesive and the type of adherand surface.

C4.7.2.6 T~icaltypesof adherandsurfaces are: wet afterpreservative treatment; dry afterpreservative treatment but unplaned before gluing; water-repellent treated.

64



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~~

S N Z NZS*3603 93 W 8583369 0010847 627 = NZS 3603: 1993

5 DESIGN OF SPECIAL STRUCTURES

5.1 Timber decking

C61 Clause 5.1 does not apply when end juints are such that each piece can be treated as continuous over its whole length, as may be the case with adequate sCar;rjóhfs or finger juints.

fhe mmen€s and deflections given by 5.1 apply on& when all pieces undergo the same def/ecthn (which fhe requirements of5.1. I and 5.2. I are intended to ensure), and therefore 2.9. I applies to these systems, as does 2.7.2.

5.1.1 General

5.1.1.1 Clause 5.1 applies to either timber decking comprised of tongued and grooved boards, nailed to the supporting members or to sawn timbers (“laminations”) nailed or spiked to each other and to the supporting members. Sawn timber laminations shall comply with the following requirements:

(a) The thickness shall not exceed 1 O0 mm;

(b) The nails or spikes fastening the individual laminations together shall be long enough to penetrate at least two and a half pieces;

(c) The nails orspikesfastening the individual laminations together shall be spaced not more than twice the depth of laminations, alternately near top and bottom edges, and staggered one- third of this spacing in adjacent laminations;

(d) Two nails or spikes shall be used to fasten each end of butt- jointed laminations to the adjacent members.

5.1.1.2 Five recognized types of lay-up are defined as follows (see also figure 5.1):

Type 1:

Type 2:

Type 3:

Type 4:

Type 5:

Simple span arrangement: all pieces bear on two supports.

Two-span continuous: all pieces bear on three supports.

Combination simple and two-span: alternate pieces in end spans bear on two supports only, adjacent pieces are continuous over two spans and bear on three supports.

Cantilevered pieces intermixed (for decks continuous over three or more spans): pieces in starter and every third course simply supported, pieces in the other courses cantilevered over the supports with end joints at alternate quarter or third points of the spans, and with each piece bearing on at least one support.

Controlled random lay-up (for decks continuous over three or more spans): distance between end joints in adjacent courses at least 600 mm, and distance between end joints in alternate courses at least 150 mm; all pieces bear on at least one support, and pieces in the first and second courses and repeating after each group of seven intervening courses, bear on at least two supports, with end joints in these two courses occurring in alternate spans or on alternate supports.

65



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~ ~~

SNZ NZS+3b03 93 85833b9 0030848 5b3

NZS 3603: 1 993

I- fa) Type l: Simple span

I F S F (b) Type 2: Two-span continuous (cl Type 3: Combination simple

and two-span

H300. mm

II I I I I I I

I I II I I I I It 1 I

(dl Type 4: Cantilever pieces intermixed

(e) Type 5: Controlled random

Figure 5.1 - Types of decking lay-up for floors and roofing

5.1.2 Uniformly distributed loads The bending moment (M) and maximum deflection (A) for decking subjected to a uniformly distributed load (wj on all bays and on alternate bays can be determined from the equations given below:

Type 1: All bays loaded:

M = wL2/8 A=SWL4/384 El

Alternate bays loaded:

M = wL2/8 A=SWL4/384 E l


M = wL2/8 A = wL4/785 EI


M = 3wL2/32 A=7wL4/768 El

........................................................................ (Eq. 5.1)

........................................................................ (Eq. 5.2)

........................................................................ (Eq. 5.3)

........................................................................ (Eq. 5.4)

........................................................................ (Eq. 5.5)

........................................................................ (Eq. 5.6)

........................................................................ (Eq. 5.7) (Eq. 5.8) ........................................................................

66



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SNZ NZS*3603 9 3 8583169 0030849 4 T T

NZS 3603: 1 993


M = W L ~ I S ........................................................................ (Eq. 5.9) ...................................................................... A = wL4/ 109 El (Eq. 5.1 O)

Aiternate bays loaded:

M = wL2/5 (Eq. 5.1 1 ) A = wL4/93 EI (Eq. 5.12)

......................................................................

......................................................................


M = ~ L ~ 1 6 . 7 A = wL4l105 EI

(Eq. 5.13)

(Eq. 5.14) ....................................................................... ......................................................................


M = ~ L ~ 1 7 . 3 ...................................................................... (Eq. 5.15) A = wL%9 EI (ES. 5.16) ......................................................................


M = ~ 1 ~ 1 6 . 7 ....................................................................... (Eq. 5.17) A = wL4 I105 EI ...................................................................... (Eq. 5.18)


M = ~ L ~ 1 6 . 7 (Eq. 5.19) A = W L ~ I 100 EI (Eq. 5.20)

......................................................................

......................................................................

where I shall be calculated from the gross cross section of the decking and Eshall be taken as 1.15 times the value given by table 2.2.

5.1.3 Point loads In the design of decking under point loads, it shall be assumed that the number of boards or laminations effectively carrying the point load is equal to the number directly contacted by the point load plus a number equal to 0.4 times the ratio of span to depth of the decking.

c5.1.3 If elastomeric adhesives are used for timber decking in accordance with 4.7.2, then wheel loads may be regardedas "transitory" in ferns of 4.7.2.1 unless the expected use of the decking concerned is such that this would be inappropriate.

5.2 Shear walls and diaphragms

C5.2 Shear walls and diaphragms are particularly suited to resisting windandseîsmk loads. niey possess substantial stiflness as well as being ductile when connected with dowel type fasteners such as nab resulting in increased load capacity and stiffness. Elastomeric or rigid glues should not be considered ductile.

67



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SNZ NZS+3b03 7 3 = 8583167 OOLO850 111 M

NZS 3603: 1 993

5.2.1 General Clause 5.2 shall apply to horizontal diaphragms and vertical (shearwall) diaphragms consisting of wood based panels nail fixed to timber framing. All sheets of panel material shall be fastened along alledges withuniformlydistributedflat head nailsto resist shearflowasshown infigure5.2.

c5.2. i For dihphmgms consisting of parallel boarding fixed to timber framing (quare sheathed diaphragms, single diagonally sheathed diaphragms or double diagonally sheathed diaphragms], refer to University of Cantenbury ReportCE89Ií Iistedunder Other Documents.

framing does not resist

Figure 5.2 - Shear flow in a panel sheathed shear wall or diaphragm

5.2.2 Design strength Designstrength fortimber framing membersand for plywood shall be in accordance with sections 2 and 6 of this Standard. Design strengths for other sheathing panels shall be in accordance with the appropriate materials standard or, where such standards are not available, shall be in accordance with the manufacturer's recommendations.

5.2.3 Fasteners

5.2.3.1 The design of fasteners shall be in accordance with section 4.

5.2.3.2 Nail sizes Nail sizes shall be chosen so as to ensure ductile behaviour under reversed cyclic loading, without brittle shank failure, sheathing break oui or premature nail withdrawal. For fully ductile design, nails shall be able to maintain ductile behaviour up to 7.5 mm nail slip during reversed cyclic loading.

C5.2.3.2 Nails should have a protective coating (such as shellac, electrqlating or galvanising) to prevent cormion. Nails shouldhave a minimum length of five times the sheathing thkkness, and be spaced at no less than 40 mm. Table 5. I indicates the maximum nail diameter if premature splitting is to be avoided in different sheathing types and thicknesses. As indicated in table 5,7, fully ductile behaviour cannot be obtained from 7.5 mm thick plywood.

58



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~

SNZ NZSa3603 93 8583169 OOLOB5L 058 W

Plywood

MDF or particle board

NZS 3603: 1 993

Sheathing thickness (mm)

4 s 7.5* 9 1W12.5 15+

2.8" 2.8" 3.3 3.3 4.0

Not suitable 3.3 4.0

" Not suitable for fully ductile design

5.2.4 Design Plywood shearwalls and diaphragms shall be designed such that design strengths of members and fastenings are not exceeded. Where shearwalls and diaphragms are required to be ductile, the ductile members or connections shall be designed to resist the over-strength forces that will be induced when anticipated displacements are imposed on the structure.

C5.2.4 Typicalload paths for diaphragms and shearwalls are indicatetiin figure 5.3, The design of conneciions, anchorages and boundaty member splices should account for any eccentricity of fasteners and concentrations of stresses.

For ductile design under earthquake loading, the nailed connection between the framing and plywood sheathing is generally designed as the ductile component, using the design nail loads from 4.2.2,

The average ultimate load that can be carried by nailed connections is approximatep 1.6 times the design strength. Hence for capacity design, an over strength factor of 1.6h 2.0

Cho!

Applied lateral load (Wl

.d'

Figure 5.3 - Distribution of loading for horizontal diaphragm and shear wall system



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SNZ NZSx3603 93 = 8583369 0030852 T 9 4

NZS 3603: 1993

should be used for design of allother components including the plywood, chords, hofd-down connections and foundations.

The design of all connections shoukj match the strength capacity of framing timber and sheathing. The designer should investbate anchorage at shearwalls, foundations and the connection of chorús and splices to ensure c0mpatibil.y with the capacity of the diaphragm when seismic forces are being resisted.

5.2.4.1 Panel nails

The design load per nail shall be determined from:

q* I- dQ” ....................................................................... (Eq. 5.21) S

where

q* =

s = nail spacing $2” =

design shear flow (applied shearlunit length) produced by the strength limit state loads

fastener design load in accordance with 4.2.2.2.

5.2.4.2 Perimeter framing members For the purposes of determining the sectional properties of timber diaphragms for in-plane flexure, the tension and compression edge chords only shall be considered, and the sheathing and the internal framing members shall be ignored. When determining the action of the connection at the base of sheatwall chord members, adequate consideration shall be given to secondary stresses that may be generated.

C5.2.4.2 Because of shear deformation and nail slip in the sheathing, the internal framing members do not contribute to the structural section properties.

5.2.4.3 Internal framing members Internal framing members shall be sized to resist face loadingsand to provide adequate nail fixing for the sheathing.

5.2.4.4 Openings Where openings are present in the diaphragm or shearwall, the shear flow interrupted by the opening shall be transmitted through the adjacent framing members into the sheathing. This requires that the trimmer members on all sides of the opening shall be continuous, or shall incorporate connections, to transmit the tension or compression over the discontinuous sections.

C5.2.4.4 Refer to “Horizontal Timber Diaphragms for Wind and Earthquakes” Smith, ûowrick and Dean. NZNSEE Bulletin Vol 19. No. 2 June 1986 for additional guidance.

5.2.5 Deflection of diaphragms and shearwalls The mid span deflection, Ah of a horizontal diaphragm acting as a simple beam, shall be calculated from:

Ah = A l + A z + A 3 ....................................................................... (Eq. 5.22)



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SNZ NZS*3603 93 = 8583369 0030853 920

NZS 3603: 1 993

where A1

A2 & = deflection of the diaphragm due to nail slip.

=

=

flexural deflection of the diaphragm considering the chords acting as a moment resisting couple deflection of the diaphragm resulting from shear deformation in the sheathing

The horizontal inter storey deflection in one storey of a shearwall, Awshall be calculated from:

A, = A4 + A s +b +A7 ....................................................................... (Eq. 5.23)

where Aq = A5 = A6 = A7 =

inter storey deflection due to chord relaxation at the base connection inter storey deflection due to shear deformation of plywood sheathing inter storey deflection due to nail slip, en, between sheathing and framing inter storey flexural deflection as a cantilever (may be ignored for single storey shearwalls).

C5.2.5 The total deflection at each level must be obtained by calculating the individual components and summing them from the base of the structure. From research work undertaken at the University of Canterbury the following are reasonable approximations for the above values, for walls and diaphragms without openings:

5 WL3 Ai =

1 92EAB2

wi 8GBt

A2 =-

(1 + a)me, 2

ACJ =

..I

......................................................................... (Eq. 5.24)

......................................................................... (Eq. 5.25)

......................................................................... (Eq. 5.26)

(Eq. 5.27) H ........................................................................... A4 = (6 , + 6f ) E

PH As =- GBt

..< .......................................................................... Eq. 5.28)

........................................................................... A~ = 2(1+ a)me, (Eq. 5.29)

2VH3 +Ho A7 =- 3EAB3

.., ......................................................................... (Eq. 5.30)

where

a = aspect ratio of each sheathing panel: = = =

O when relative movement along sheet edges is prevented, i when square sheathing panels are used, 2 when 2.4 x 1.2 m panels are orientated with the 2.4 m length parallel with the diaphragm chords ( = 0.5 alternative orientation)

A = sectional area of one chord ( m d ) B = distance between diaphragm chord members (mm) en = nail slip resuking from the shear force V(mm) (ref. 4.2.2.3)



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S N Z rJZSr3b03 93 8583Lbï 0030854 867

NZS 3603: 1 993

E = G = H = L = m = P = t = v = w = 8 = 6, =

ebstic modulus of the chord members (MPa) shear modulus of the sheathing (MPa) height of the storey under consideration (mm) span of a horizontal diaphragm (mm) number of sheathing panels along the length of the edge chord inter storey shear force (N) thickness of the sheathing (rnm) shear force in the storey under consideration (N) lateral load applied to a hotizontal diaphragm (N) flexural rotation at the base of the storey under consideration (radians) ver t id movement that accompanies compressive strain at one end of the wall. (Typically dc= 0.3 Cmm where Cis axial chod compression (kN) in single storey shearwall with end bearing on the bottom plate.) vertical movement that accompanies tensile strain at the other end of the wall. (dtmay range from 2 Trnm where the restraint is provided toa bottom ptate member to 0.2T mm where the chord is directly anchored to a rigid foundation and T= resultant tensile chord uplift (kN))



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SNZ NZSa3b03 73 H ô5ô3Lb9 0030855 7T3

NZS 3603: 1993

6 PLYWOOD

6.1 General

6.1.1 Section6appl¡estoconstruction plywoods manufacturedand graded according to the requirements of ASNZS 2269.

6.1.1.1 Calculations of member strength and stiffness shall take account of the different contributions of veneers parallel and perpendicular the face and back veneers with respect to the direction of stress. Calculation methods and data for standard constructions of plywood are in AS/NZS 2269 and in 6.2.2 and 6.3.5.

6.1.1.2 Section 6 applies to the derivation of design stresses for plywood. Design methodsfor elements such as web beams and stressed skin panels are in text books (see 6.6). For design of end or edge joints in plywood refer to Appendix J.

(26.1. I A W Z S 2269 is a new joint New Zealand-Australian Standard expected to be published in December 7993 (to supersede NZS 3614).

6.1 -2 Plywood shall have a durability appropriate to the specified end use environment. Veneers shall be of a species of an appropriate natural durability or shall have preservative treatment to NZMP 3640.

6.1.3 Where plywood is exposed to environmental conditions that raise its moisture content to above 20 %for prolonged periods, only Type A bonds as defined in AS 2754.1, and AYNZS 2269, shall be used.

6.1.4 Grades of plywood Visual qualities of plywood shall be assigned a stress grade according to AS/NZS 2269.

6.1.4.1 Radiata pine plywood stress grades Visual veneer qualities A, B, S, C, and D are defined in AS/NZS 2269.

Radiata pine plywood made with C, D or S quality veneer is F11 stress grade. A or i3 quality veneers are F14 stress grade.

Most plywood made from radiata pine contains some C or D grade veneers and is therefore F11 grade. However when higher quality faces and backs are used, properties may be calculated using transformed sections or similar methods, as described in AS/NZS 2269, to allow for the higher stress grade veneers.

6.2 Stresses and moduli

6.2.1 Characteristic stresses and moduli Characteristic stresses and moduli for plywood and veneer stress grades are given in table 6.1 for dry use. For other plywoods and grades outside this range refer to AS/NZS 2269.



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~ ~

SNZ NZSa3603 93 = 8583369 OD3085b b3T

Bending

fpb

NZS 3603: 1993

Tension Panel Shear

fPf fps

Stress grade

57.6 44.5 36.7 28.8 22.5

F22 F17 F14 Fí 1 F8

C6.2.1

34.6 6.0 26.7 6.0 22.0 5.4 17.3 4.7 13.5 4.2

Table 6.1 - Characteristic stresses for structural plywood (MPa) (Moisture content 15 % or less)

Rolling Shear

fpr

2.4 2.4 2.2 1.9 1.7

Compression in the normal plane to the of the plane of sheet the sheet

fPC fPP

Modulus of

elasticity

E

16000 14000 12000

21.6 10500 16.9 91 O0

Modulus

rigidity

525 455

These are interim soff conversion values pending results from an in-grade test programme.

6.2.2 Section properties The net section properties shall be calculated according to the methods prescribed in AS/NZS 2269 and Appendix F of this Standard.

C6.22 Refer Chapter BI O of the Timber Use Manualormanufacturers’literature for section property data. ASNZS 2269 does not include the shearproperty, Q.

6.3 Modification factors

6.3.1 Modification factors for the design of plywood components shall be taken from the relevant clauses in section 2 and section 6.

6.3.2 Duration of load Use the factors kl and k2 in 2.7.

6.3.3 Moisture content Where plywood is in an environment that raises the average moisture content above 15 %for the maximum load case, use the modification factor k14 in figure 6.1.

C6.3.3 Dry locations include panels inside buildings, most floors, and external panels continuously protected from the weather by a coating system. Wet locations include tanks, fluming, retaining walls, formwork, and applications subject to high humidity. Moisture content for plywood is generally a % or so lower than solid wood in a dry environment.

74



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SNZ NZSx3b03 93 8583369 0030857 576

NZS 3603: 1 993

1.0 $:

4- & 0.9 o )i 0.8

E 0.7

0.6

3 0.5 Ir

0.4

c E p>

O o L 3

O

c

15 16 17 18 19 20 21 22 23 24 25 26 Plywood moisture content (%I

Modulus of elasticity Tension

Bearing modulus of rigldity

Bending, shear

Compression

Figure 6.1 - Moisture content factor, k14

6.3.4 Temperature Clause 2.1 1 shall apply.

6.3.5 Face grain angle Where plywood is stressed with the face grain at an angle to the direction of stress, for bending, compression and tension, the section property parallel to the face grain ( I i ,Z l , Ai) with factors k15 for strength and k16 for stiffness as given in tables 6.2, 6.3 shall be used. For shear, the appropriate cross section property and the factors in table 6.4 shall be used. The angle that the face grain makes with a cut edge at the point of highest stress shall be used. Forgoo, the section properties perpendicular to the face grain may be used without k15 and kl6.

6.3.6 Rolling shear with stress concentration For plywood glued to framing members, kl7 shall be 0.5 when the framing is adjacent and parallel toacut edge,orshall bedeterminedfromstressanalysisat thecut edge. kl7appliesonlyto rolling shear.

C6.3.6 The Canadian code CAN3 086 includes thisanalysis as a flange web shear factor for Doughs fir plywood. An amendment could include this at a later date.



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~~

SNZ NZS*3603 93 8583Lb9 OUI10858 402

I

I1 II 3 PlY 0.96 1 .o 0.44 0.18 0.10 0.07 0.07 0.09 4 Pb 0.88 1 .o 0.45 0.18 0.11 0.09 0.12 0.19 5 PlY 0.80 1 .o 0.45 0.19 0.12 0.11 0.17 0.31 7 PlY 0.72 1 .o 0.45 0.20 0.13 0.13 0.23 0.45 9 PlY 0.68 1 .o 0.46 0.20 0.14 0.15 0.27 0.54

NZS 3603:1993

Table 6.2 Face grain orientation factor, &i5 for strength

Face grain angle (degrees) Layup fe I t O 15 30 45 60 75 90

Compression

4 PlY 0.50 1 .o 0.83 0.66 0.60 0.66 0.83 1.00 7 PlY 0.57 1 .o 0.81 0.62 0.56 0.59 0.73 0.85 5 PlY 0.60 1 .o 0.80 0.60 0.54 0.57 0.69 0.79 3 PlY 0.67 1 .o 0.77 0.56 0.50 0.51 0.60 0.66

Tension and in-plane bending

4 PlY 0.50 1 .o 0.69 0.49 0.43 0.49 0.69 1.00 7 PlY 0.57 1 .o 0.64 0.44 0.38 0.42 0.57 0.77 5 PlY 0.60 1 .o 0.62 0.42 0.36 0.40 0.53 0.68 3 PlY 0.67 1 .o 0.58 0.38 0.32 0.34 0.43 0.52

Bending flat

Il II 3 PlY 0.96 1 .o 0.45 0.22 0.13 0.09 0.08 0.07 4 PlY 0.88 1 .o 0.52 0.31 0.23 0.20 0.18 0.18 5 PlY 0.80 1 .o 0.56 0.35 0.29 0.32 0.38 0.43 7 PlY 0.72 1 .o 0.61 0.40 0.34 0.38 0.50 0.65 9 PlY 0.68 1 .o 0.63 0.42 0.36 0.41 0.56 0.74

Table 6.3 Face grain orientation factor, &I6 for stiffness

Face grain angle (degrees) Layup te I t O 15 30 45 60 75 90

Compression, tension and in-plane bending

4 PIY 0.50 1 .o 0.47 0.23 0.18 0.23 0.47 1.00 7 PlY 0.57 1 .o 0.46 0.22 0.16 0.19 0.37 0.77 5 PlY 0.60 1 .o 0.46 0.21 0.15 0.18 0.34 0.69 3 PlY 0.67 1 .o 0.46 0.20 0.14 0.15 0.26 0.53

Bending flat

* This column is for veneers of equal thickness; for other layups calculate tdt (ratio of parallel veneer to total thickness) or I1lIgrocc (Igrocs = bt3/lí!) and use thisvalue to interpolate within the table.



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NZS 3603: 1 993

Table 6.4 Face grain orientation factors for shear

Parallel or perpendicular to the face grain k15=k16 = 1.0 Rolling shear strength at 45 degrees to the face grain k15 = 1.3 Panel shear strength at 45 degrees to the face grain k15 = 1.5 Panel shear stiffness at 45 degrees to the face grain k16 = 3.0

6.3.7 Panel shear framing support Forpanelsframedonfoursidesbyframing, k18=l .O. Forpanelsframedontwosides, k18 = 0.89.

C6.3.7 In a box beam With stiffened webs, plywood is supported on four sides. In an unstiffened I beam or in truss gussets it is supported on two sides on&.

6.3.8 For plywood loaded in-plane, the stability factor, k8 shall be determined from Appendix H. This method is conservative and a more rigorous alternative method in AS 1720 Appendix E may be used.

6.4 Loading perpendicular to the plane of the sheet

6.4.1 Strength

6.4.1.1 Bending strength The bending strength of plywood loaded perpendicular to the plane of the sheet shall satisfy

Me< #Mn ......................................................................... (Eq. 6.1)

where

#Mn = design strength of member in bending # = strength reduction factor M* = design bending moment

Mn = nominal strength of member in bending.

The nominal bending strength for plywood loaded perpendicular to the plane of the sheet shall be taken as

......................................................................... (Eq. 6.2) Mn = kl kl4kl5klSfpbZn

where

kl ,kl4,k15 = modification factors given in section 2 or 6.3 kl9 = 1.2 for 3-ply bending perpendicular to span, 1 .O for all other plywood

= characteristic bending stress given table 6.1 = net section modulus of the plywood sheet as in 6.2.2 (Z7 or Z2 as applicable)

fPb Zn

6.4.1.2 Shear (rolling) strength The rolling shear strength of plywood loaded perpendicularto the plane of the sheet shall satisfy

v T ~ qvnr ......................................................................... (Eq. 6.3)

where

#Vnr = # = strength reduction factor

design rolling shear strength



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NZS 3603: 1 993

Vr* = design shear force Vnr = nominal rolling shear strength

The nominal rolling shearstrength for plywood loaded perpendiculartothe planeof thesheet shall be taken as

......................................................................... (Eq. 6.4) vnr = kl kl4k15fprb YQ

where

kl ,kl4,k15 = = = b

UQ =

modification factors given in section 2 or section 6.3 characteristic rolling shear stress given in table 6.1 width of panel or width of stressed region as shown in figure 6.2 shear constant, with land Q calculated as in 6.6.2.3 using 11 and QI or 12 and 02 as applicable

fpr

6.4.1.3 Bearing strength The bearing strength of plywood loaded perpendicular to the plane of the sheet shall satisfy

Nb 5 4Nnb ......................................................................... (Eq. 6.5)

where

4Nnb = design bearing strength @ = strength reduction factor N i = design bearing load Nnb = nominal bearing strength

The nominal bearing strength for plywood loaded perpendicularto the plane of the sheet shall be taken as

......................................................................... (Eq. 6.6) Nnb = kl kkl4fpp4p

where

kl ,k,k14 = = = bearing area

modification factors given in section 2 or clause 6.3 characteristic compression stress normal to plane of sheet given in table 6.1 fpP

AP

6.4.2 Deflection Deflections shall be calculated from standard bending and shear formulae using:

EI = kl 4 kl &I1 ......................................................................... (Eq. 6.7) k2

where

......................................................................... (Eq. 6.8)

the effective bending stiffness, calculated as in 6.2.2 the effective shear stiffness modification factors given in section 2 or clause 6.3 second moment of area parallel to the grain width of panel total thickness of panel short term modulus of elasticity from table 6.1 short term modulus of rigidity from table 6.1



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NZS 3603:1993

6.5 Loading in the plane of the sheet

6.5.1 Strength

6.5.1.1 Bending strength The bending strength of plywood loaded in the plane of the sheet shall satisfy

M: I ØMnj ......................................................................... (Eq. 6.9)

where

ØMnj = design in-plane bending strength 4 = strength reduction factor M; = design in-plane bending moment Mni = nominal in-plane bending strength

The nominal in-plane bending strength for plywood loaded in the plane of the sheet shall be taken as

Mn j = kl k8 kl4k15 fp&d */6 ....................................................................... (Eq. 6.10)

where

k1 ,kl4,kl5 = modification factors given in section 2 or 6.3 k8 = stability factor given in 6.6.5

= characteristic bending stress given in table 6.1 = effective panel thickness te = thickness of plies parallel to direction of stress

d = depth of panel in bending

f i b

6.5.1.2 Tension strength The tension strength of plywood loaded in the plane of the sheet shall satisfy

4 5 Writ ....................................................................... (Eq. 6.1 1)

where

QNnt = design tensile strength 4 = strength reduction factor Ni = design tensile force N,, =. nominal rolling shear strength

The nominal tensile strength for plywood loaded in the plane of the sheet shall be taken as

....................................................................... (Eq. 6.12) Nnt = kl kl4kl 5fptted

where

kl ,kl4,kl5 = = = effective panel thickness te =

d = depth of panel

modification factors given in section 2 or 6.3 characteristic tension stress given in table 6.1

thickness of plies parallel to direction of stress

f i t



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NZS 3603: 1 993 -

6.5.1.3 Compression strength The compression strength of plywood loaded in the plane of the sheet shall satisfy

~ * c W n c ....................................................................... (Eq. 6.13)

where

#Nnc = design compressive strength $J = strength reduction factor N c = design axial compressive load N,, = nominal compressive strength

The nominal compressive strength for plywood loaded in the plane of the sheet shall be taken as

(Eq. 6.14) Nnc = kl k8kl4kliEifpcted .......................................................................

where

kl ,k14,k15 = ka = stability factor given in 6.6.4

= = effective panel thickness te =

d = depth of panel

modification factors given in section 2 or 6.3

characteristic compression stress given in table 6.1

thickness of plies parallel to direction of stress

rpc

6.5.1.4 Panel shear The shear strength of plywood loaded in the plane of the sheet shall satisfy

qVnj ....................................................................... (Eq. 6.15)

where

$Vnj = design panel shear strength 4 = strength reduction factor V; = design panel shear force Vni = nominal panel shear strength

The nominal panel shear strength for plywood loaded in the plane of the sheet shall be taken as

where

....................................................................... (Eq. 6.16)

kl to k18 = k8 =

= = total panel thickness t

d = depth of panel

modification factors given in section 2 or 6.3 stability factor given in 6.6.4, but used with the alternative method in 6.3.8 characteristic shear stress given in table 6.1 f i s

80



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NZS 3603: 1 993

6.5.2 Combined stresses

6.5.2.1 Combined compression, bending and shear shall satisfy:

[A) + [ KT + [ ”) < 1.0 ....................................................................... (Eq. 6.1 7) W n c $Mni 4 Vni

6.5.2.2 Combined tension, bending and shear shall satisfy:

....................................................................... (Eq. 6.18)

6.5.3 Deflection Deflections shall be calculated from standard bending and shear formulae using:

EI=--- k14k16 E - k* 12

k14k16 Gtd GA=-

....................................................................... (Eq. 6.19)

....................................................................... (Eq. 6.20)

where

EI = effective bending stiffness GA = effective shear stiffness k2,k14,k16 = modification factors given in section 2 or 6.3 E = short term modulus of elasticity from table 6.1 G = short term modulus of rigidity from table 6.1 t = total panel thickness te = effective panel thickness d = depth of panel

6.6 Plywood components

6.6.1 General The design of specific items such as box beams, stressed skin panels etc. shall incorporate the material resistances from the clauses above for plywood, relevant provisions in this clause pertaining to jointing and design details, and material resistances for the other materials used in the construct ion.

6.6.2 Component design

6.6.2.1 The resistances and stiffnesses of each component shall be calculated allowing for the different properties of the materials (e.g. plywood and timber), using section properties transformed according to their elastic moduli as outlined below, or using a similar approach. Criflical sections in some components are illustrated in figure 6.2.

C6.6.2.1 Design methods are outlined in literature available from a number of manufacturers, associations and in the Timber Use Manual.

81



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~

SNZ NZS*3b03 73 8583Lb7 00LO8b4 706

NZS 3603:1993

Face grain parallel to span Face grain perpendicular to or at 45" to span

(a) Plywood acting as a beam

(bl Stress transfer in stressed skin panels

b

IC) Stress transfer in plywood web beams

Figure 6.2 - Critical sections in some plywood components

6.6.2.2 Bending Design bending strength at a section in a flexural component shall satisfy

M* S #Mn ....................................................................... (Eq. 6.21)

where

M* = design bending moment #Mn = design bending strength # = strength reduction factor M,, = nominal bending strength

The nominal bending strength M,, is the minimum bending strength determined when each part of the section is checked with an equation of the form

M, = MZ,, ....................................................................... (Eq. 6.22)

where

k = relevant modification factors f = characteristic bending stress of part being considered Zef = effective transformed section modulus = Z€I/(€,yj) X i 3 Ei = elastic modulus of the part being considered Yi

=

=

total sum of fIof the individual parts of the component

distance from the neutral axis to the point farthest from the neutral axis in the part being considered.

82



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NZS 3603: 1 993

6.6.2.3 Axial load

The design axial strength at a section in a component shall satisfy

N* I @Nn ....................................................................... (Eq. 6.23)

where

N* = design axial load $Nn = design axial strength $ = strength reduction factor N, = nominal axial strength

The nominal axial strength N, is the minimum axial strength determined when each part of the section is checked with an equation of the form

N, = MA,, ....................................................................... (Eq. 6.24)

where

k = relevant modification factors f = characteristic axial stress of part being considered A,# = effective area = X A E j ZEA Ei

= =

total sum of €A of the individual parts of the component elastic modulusof the part being considered where the strength is being determined.

6.6.2.4 Shear The design shear strength at a section in a flexural component shall satisfy

v i < 4Vn ....................................................................... (Eq. 6.25)

where

V; = design shear force @Vn = design shear strength @ = strength reduction factor

V, = nominal shear strength

The nominal shear strength Vn is the minimum shear strength determined when each part of the section is checked with an equation of the form

Vn = MW IIQ ....................................................................... (Eq. 6.26)

where

k = relevant modification factors f Q W = width of the shear surface IIQ

= =

=

characteristic rolling or panel shear stress of part being considered area outside the section multiplied by its lever arm about the neutral axis

CEIILEQ where ZfQ is the sum of the EQ of only the required first moments of area of the parts outside the section being considered and X I is the total sum of €I of the individual parts of the component.

6.6.2.5 Deflections Deflection calculations for plywood components shall make due allowance for bending and shear deformation, joint slip and creep. Bending stiffness EI and shear stiffness GA shall be



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S N Z NZS*3b03 9 3 m 85831b9 00108bb 589

NZS 3603: I 993

determined from the sum of the El's and GAS of the individual parts of the component. Deflections may be calculated using standard engineering formulae.

6.6.3 Plate action If plywood bending perpendicular to the face grain is supported on four edges, Appendix G may be used to allow for plate action.

6.6.4 Stability

6.6.4.1 General Design of plywood components shall make allowance for the stability of the whole and each part of the component using the stability factor k8.

6.6.4.2 Plywood Factor shall be determined from 6.3.8. For stressed skin panels loaded directly on the compression skin, stability need not be assessed ifdeflectionsof the skin are less than spadl 80, assuming simple support conditions in simple beam theory.

6.6.4.3 Other parts The stability of each part of a component shall be determined from appropriate material standards. In web beams and diaphragms, the stability of the flange timber under load reversal and compression buckling should be calculated in accordance with 2.1 O.

C6.6.4 A method for calculating stability factors for webbed beams is given in Chapter BIO of the Timber Use Manual.

6.6.4.4 Stiffeners in web beams The recommended distance between vertical stiffeners, L', in flexural components is given by figure 6.3, for locations where the applied shear is equal to the design shear strength. Where the applied shear is less, the spacing, Ls may be increased to:

... (100- Ps) L s = L S ( l+ 25 ) ................................. Eq. 6.27)

where p is the applied shear ($1 as a percentage of the design shear ( Vn), provided that ps shall not be taken as less than 50 %. The maximum value of Lc shall be 3 íS or 3hw.

84



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SNZ N Z S + 3 6 0 3 9 3 8583369 0030867 435 W

1200 n E E ,1000 .$

v)

800 C m - c

NZS 3603: 1 993

-

-

-

C Q 600 I n g 400

-cr 200

+ al

c m v) +

L m o)

o -

-

-

-

Plywood web thickness

l5 mm } 5 ply

mm } 3 ply

12.5 mm

7.5 mm

0 1 I I # 1

O 200 400 600 800 1000 1200 1400 1600 1800 2000

Distance between stiffeners, íi, (mm)

Figure 6.3 - Stiffener spacing for plywood webs in flexural components

6.6.5 Nailed and screwed joints in plywood

6.6.5.1 General Refer to 4.2.2.2,5.2.3 and 5.2.4. Provisions for nails can be applied also to screws of the same shank diameter.

6.6.5.2 Spacing of nails in plywood Spacing of nails and screws in plywood is normally controlled by the limits on spacings in framing timbers. Nails shall not be closer than 3 nail diameters to the edge of the sheet.

6.6.5.3 Nails in withdrawal Permanent axial loading of nails is not recommended. Withdrawal loads for nails and screws shall be as for solid timber of the same species.

6.6.6 Other mechanical fasteners Other fasteners may be used with plywood (bobs, staples etc) provided suitable test data and design procedures are applied.

6.6.7 Glued interfaces

6.6.7.1 General Structural glued joints between plywood and timber framing shall comply with 4.7.



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SNZ N Z S * 3 6 0 3 73 8583167 0010868 351

NZS 3603: 1 993

C6.6.7.7 Nail gluing For nail gluing ofplywood to fmming timber, nails should be spced at not more than 75 mm with panels less than 1 Ornm thickand no more than 1 O0 rnm for ofherpaneis. There should be a row of nails for each 50 mm nominal width of framing timber. Nails should have a large head and should be at least three times the plywood thickness in length.

6.6.7.2 Load capacity of a jointed interface The strength of a jointed interface shall satisfy

....................................................................... (Eq. 6.28) V; 5 W n c i

where

Vb = design shear force $Qnsi = design strength of the joint Q = strength reduction factor Qnsi = nominal strength of the joint

For a glued joint the nominal strength of the joir.. can be taken as the lesser of

Qnci = kl kl4kl5kl7fshw r/Q ....................................................................... (Eq. 6.29)

or

QnSi = kl k l 4 f s ~ UQ ....................................................................... (Eq. 6.30)

and for a nailed joint the nominal strength of the joint can be taken as

kQkwvQ .....

S Qnsi =

where

......................... ......................................... (Eq. 6.31)

load duration factor characteristic rolling shear stress fs,or panel shear stress fpsfor plywood from table 6.1 as applicable characteristic shear stress for timber from table 2 nominal strength of a nail from 4.2.2 effective shear area, calculated as in 6.6.2.4 or 2/3bdfor a rectangular section of uniform €glued at neutral axis nail spacing for a single row of nails modification factors given in 6.3



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Category Minimum

NZS 3603:1993

r, ff fe fs fP E

7 ROUND TIMBERS

High Normal

7.1 General

450 52 31 25 3.5 7.7 12.1 350 38 23 16 3.1 6.4 8.7

7.1.1 Whether naturally round timbers are used as simple structural members, that is as poles or piles, or as elements of a composite structure, the design procedure shall be similar to that given in section 3, Design of structural members, subject to the provisions of 7.2 and 7.3.

7.1.2 Naturally round timber shall be assumed to be in the green or dry condition according to its moisture content at the time of fabrication or installation and in service as shown in table 2.1 except that timbers in ground contact shall in all cases be assumed for design purposes to be in the green condition at the ground line.

7.2 Characteristic stresses and elastic moduli The characteristic stresses and elastic moduli for logs, poles, or piles conforming in quality to the requirements of NZS 3605 shall be as given by table 7.1. For Australian timbers the values given by the limit states version of AS 1720 shall be used. The supplier of poles in the high density category shall either:

(a) Provide evidence that the poles have an outer density exceeding the minimum value specified, or

(b) Subject the poles to the proof testing requirements of NZS 3605.

Table 7.1 - Characteristic stresses (MPa) and modulus of elasticity (GPa) for naturally round softwood timber in green condition

I Outer zone density, kg/m3 1 Property

7.3 Design

7.3.1 Round timber members shall be designed using the procedures outlined in section 3 subject to the additional requirements of 7.3 to 7.6 and changes to the appropriate section properties.

c7.3. i The effect of 7.3.1 is that design strengths for naturally round timbers are obtained by moúífying the characteristic stresses of table 7.7 in the same way as for sawn tjmbers but with three additional modification factors where applicable.

7.3.2 The slenderness coefficient, Sfor the calculation of stability factor, k8 as used in 3.3.2 for round members in axial compression is defined as:

S= L l d p

where

L = length between points of lateral restraint = mean of diameters at points of lateral restraint. dP



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SNZ N Z S x 3 b 0 3 93 8583369 0010870 TOT

NZS 3603: 1 993

7.4 Modification factor, k20 for trimming or shaving The characteristic stress and the modulus of elasticity shall be multiplied by the appropriatevalue of k20 as given by table 7.2 according to the method used to remove the bark. Where a naturally round timber is shaved to a smooth cylindrical or tapering form, as permitted by NZS 3605, or where a slab is removed to provide a flat bearing surface, it shall be considered to be machine shaved. Where the machine used to remove bark follows the pole contours it shall be considered to be machined peeled.

Table 7.2 - Peeling or shaving factor, k20

Applied to Machine peeling Machine shaving

fb or ft 0.90 0.85 fc , $ or fs 1 .o0 1 .o0 E 1 .o0 0.95

c7.4 The characteristic stresses andmoduliof elasticity given in table 7.1 are applicable when the processes of branch trimming and bark removal cause no more damage, especially associated with knot whorls, than occurs in carefully prepared hand-peeled or hydraulically debarked poles.

7.5 Modification factor, k21 for preservative treatment involving steaming For timber treated by the alternating pressure method or by the oscillating pressure method, the characteristic stress and the modulus of elasticity shall be multiplied by the appropriate value of k21 as given by table 7.3.

c7.5 These pressure treatments involve steaming of the timber. Details of the treatment are given in Timber Preservation Council specifications.

Table 7.3 - Steaming factor, k21

Applied to k21

0.85 0.90 0.95

7.6 Modification factor, k22 for dry use conditions For poles or parts of poles that are dry (see 7.1.2), the characteristic stress and the modulus of elasticity shall be multiplied by the appropriate value of k22 as given by table 7.4.

Table 7.4 - Dry use factor, k22

I Applied to k22

1.25 1 .o6 1.12

7.7 Effective sections Section properties shall be calculated from the diameter at the critical section.



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SNZ NZSm3603 93 8 5 8 3 1 b î 0010871 946 W

NZS 3603: 1 993

8 GLUED LAMINATED TIMBER

8.1 Scope Section 8 covers the design of glued laminated timber members manufactured in accordance with NZS 3606.

8.2 Specification The information supplied by the designer to the manufacturer of a glue laminated member shall include the following:

(a) Length, depth, width and shape of the member;

(b) Camber;

(c) Number, thickness, grade, species, and arrangement of laminations;

(d) Limitations on placement of butt joints (if used);

(e) Exposure category and service equilibrium moisture content;

(f) Preservative treatment (if any);

(9) Surface finish;

(h) Moisture content.

C8.2 Exposure categories and corresponding adhesives are specified in NZS 3606, section 5. Exposure categories defined therein are:

Category A (interior): In buildings provided wifh ventilation and with heat either whole orpart- time and where the timber is permanently below 18 % moisture content, for example, houses and offices.

Category B (occasionaiiy damp). In buildings with warm and damp conditions or vely wide cyclical variations of temperature and humidity, such as laundries and dye works. Exposed to exterior atmosphere but sheltered from direct sun and min, such as open sheds, poches and exposed beam under soffits.

Category C (fully exposed): &posed directly to sun and rain, or in buildings with very high humidity such as wool scouring plants.

8.3 Standard sizes

8.3.1 Standard widths of horizontally laminated members (or depths of vertically laminated members) should be used.

C8.3.7 Standard widths are shown in table 8.1 when in the finished condition.

8.3.2 Standard thicknesses of laminations in straight members are:

(a) 45 mm if obtained from 50 mm call size laminations;

(b) 19 mm if obtained from 25 mm call size laminations.

89



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SNZ NZS13603 9 3 8583369 0030872 882

NZS 3603: 1 993

Laminations ex call

dimension mm

Standard or Premium finish utility finish

mm mm

8.3.3 Standard thicknesses for curved members, and the corresponding recommended minimum radii of curvature are shown in table 8.2.

Net thickness of laminations

Thickness mm

Members with Members with constant curvature tangent ends

Radius Radius mm mm

8.4 Finish Three levels of finish: utility, standard and premium are specified in NZS 3606 to cover the normal range of requirements.

C8.4 Utility finish should be used where the member is not seen or where appearance is unimportant, or where the surface irregularities do not impair the fabrication of the total structure. Standard finish should be used as the normal finish for glue laminated timber members exposed to view and should have a finish suitable for painting, staining or clear finishing. Premium finish is the highest quality of finish and is intended for demanding situations such as handrails and table tops, where close visual and tactile examinations will be encountered; it is comparable to scraping and fine sanding on cabinet andjoinery work.

8.5 Moisture content In the determination of design strengths, the moisturecontent shall be considered to be that which exists when the member receives its full design load. The timber shall be considered to be in the dry condition when it has a moisture content less than or equal to 1 8 % and in the green condition when it has a moisture content greater than or equal to 25 %. The characteristic stress for timber in a condition between wet and dry shall be obtained by linear interpolation.

90



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SNZ N Z S w b 0 3 93 8583369 0030873 719

NZS 3603:1993

8.6 Design The stresses and elastic moduli for sawn timber set out in section 2, and the design procedures set oui in section 3 shall apply to glued laminated timber members subject to the additional requirements of 8.7 to 8.12 inclusive.

8.7 Modification factors

8.7.1 Vertically laminated timber

8.7.1.1 For a member of rectangular cross section comprising two or more laminations securely fastened together by gluing and loaded in a direction parallel to the plane of the gluelines, the characteristic stress in bending, tension, shear and compression parallel to the grain may be increased by the parallel support factor, kíj given in table 2.7. In the use of this table, the number of elements carrying a common load shall be taken as the total number of laminations in the member for bending, tension and shear. For compression parallel to the grain, the number of elements shall be taken to be equal to the total number of laminations for the case of buckling in the plane of the laminations, and half of the total number of laminations for the case of buckling out of the plane of the laminations.

8.7.1 -2 If several vertically laminated members act together to form a parallel support system as described in 2.9.1, then the effect of load sharing on bending shear and compression stress may be obtained by taking the number of elements to be the total number of laminations in the several glued laminated members.

8.7.2 Horizontally laminated members

8.7.2.1 For a member of rectangular cross section comprising two or more laminations securely fastened together by gluing and loaded in a direction perpendicular to the plane of the gluelines, the characteristic stresses in bending, tension, compression and shear parallel to the grain may be increased by the parallel support factor, k(3 given in table 2.7. The number of elements which support the common load shall be taken to be 1 .O, 0.5 and 0.25 times the number of laminations in a member when evaluating k6 for application to the characteristic stress of tension members, the compression stress of columns and the bending stress of beams respectively. Linear interpolation shall be used in table 2.7 as necessary. In evaluating k6 for modifying the characteristic shear stress of beams, the effective number of elements for shear shall be taken as four or the number of laminations, whichever is the lesser.

8.7.2.2 If several horizontally laminated members act together to form a parallel support system as described in 2.9.1, then the Characteristic bending and compression stresses may be further multiplied by factor, where the number of elements is the number of horizontally laminated members carrying the common load.

C8.7.2 The factor is applied to the characteristic stresses for solid timber and is intended to account for the effects of glue laminating. Hence it is not used when the characteristic stresses for glulam elements ha ve been derived directly through the testing of such glulam elements.

8.7.3 Combination of species or grades of timber

8.7.3.1 In determining the stress due to bending in interior laminations of grades or species having lesser mechanical properties than the exterior laminations, a linear strain distribution shall be assumed.

91



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SNZ NZS*3603 9 3 m 8583169 0030874 655

NZS 3603: 1 993

8.7.3.2 The gross section properties of such a member shall be obtained by the method of transformed areas, whereby the effective width of each lamination is given by:

b,- Ei b(eff) = - Eo

(Eq. 8.1) .........................................................................

where

bi = actual width of the i th lamination €i = modulus of elasticity of the ith lamination Eo = modulus of elasticity of the outermost lamination in tension.

CB. 7.3.2 Lamination of species with widely differing shrinkage or elastic properfies may result in high shear stresses at the gluelines.

8.7.4 Creep deformation Allowance for creep effects in glued laminated members shall be considered asdescribed in 2.7.2 except that a value of 1.5 may be taken for the duration of load factor, k2 for deflection instead of the value 2.0 specified for sawn timber (for dry members subjected to long duration loads).

8.7.5 Curvature For the curved portion of horizontally laminated members, the characteristic stress in bending shall be multiplied by a factor k23:

........................................................................ (Eq. 8.2)

where

te = lamination thickness ß = radius of curvature of innermost lamination.

8.7.6 Method of grading For glued laminated members made from machine graded F6 (or No. 1 framing) grade radiata pine, the modulus of elasticity value from table 2.3 may be multiplied by 1.12.

C8.7.6 NZS 3606 excludes pith from F6 (or No. 1 framing) grade radiata pine when useâ in the outer laminations of horizontally laminated members. This increases the effective stiffness of these members by placing timber of higher stiffness in regions of higher stress. Machine grading pmvjdes a more precise control of modulus of elasticity than does visual grading, likewise allowing an increase in design values.

8.7.7 Size factor The characteristic stresses in bending and tension shall be multiplied by the size factor, k24 as given in equation 8.3:

k24 = (300 / d)O*’ 67 ......................................................................... (Eq. 8.3)

where d = depth of a beam or twice the width of a tension member.



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SNZ NZSx3b03 93 85831b9 0010875 591

NZS 3603: 1993

Maximum depth of beam or twicewidthoftension member

mm

C8.7.7 lhe size factor for beams refers to beams of solid glulam. Forbuilt up beams the size factor shaltbe applied to the individual component; an example of this wouldbe the tension flange of a box beam. Table 8.3 gives values of k24 for members up to 1500 mm,

300 375 500 625 750 1000 1250 1500

Value of k24 1.0 0.96 0.92 0.89 0.86 0.82 0.79 0.77

8.8.1 Radial stress in curved members If the bending tends to increase the radius of curvature then, to prevent tensile splitting

........ .............. ............ ....... ................ ......... ......... (Eq. 8.4)

and if the bending tends to decrease the radius of curvature then, to prevent a compression failure perpendicular to the grain

where

M* = Ø = kl = k 4 = R = b = d = fs = f p =

......................................................................... (Eq. 8.5)

the design bending moment strength reduction factor duration of load factor for strength as given in section 2 load sharing factor for number of beams, as given in section 2 radius of curvature at mid-depth of section member breadth member depth characteristic shear stress characteristic bearing stress perpendicular to the grain.

8.8.2 Pitched cambered beams (see figure 8.1)

8.8.2.1 The radial stress induced by bending in a pitched cambered beam of rectangular cross section is a maximum near the mid-depth of the apex and shall be controlled by 8.8.1, and if the bending tends to increase the radius of curvature then, to prevent tensile splitting:

* k k bd2 M 1Ø-fS-- k25 l8

.................................................................................. (Eq. 8.6)

if the bending tends to decrease the radius of curvature then, to prevent a compression failure perpendicular to the grain:

k k bd2 M* I Ø > f , - k25

................. .................................................................. (Eq. 8.7)



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NZS 3603: 1 993

where

d d2 k25 = + k27 E' k28 3 ....................................................................... Eq. 8.8)

or is read from figure 8.1 with k26, k27 and k28 from table 8.4.

UJ ni

Y

0.20

0.15

0.10

0.05

O O 0.1

/

7

/ /

0.2 0.3 0.4 0.5

Figure 8.1 - Determination of k25 factor for pitched beams



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NZS 3603: 1993

Table 8.4 - Values of constants for calculation of radial stresses in pitched beams

Slope of upper surface of beam

(degrees) ~

2.5 5 7.5

10 15 20 25 30

Value of constant

k26 k27 k2a

0.008 0.01 7 0.03 0.04 0.06 0.09 0.1 2 0.16

0.17 0.13 0.09 0.08 0.06 0.06 0.06 0.06

0.13 0.19 0.23 0.21 0.17 0.14 0.12 0.1 1

8.8.2.2 The bending stress at the cross section through the apex of a pitched beam is a maximum at the soff it and shall satisfy

M* 2 @k,k4k6k8k24fb2(1+ 2.7tana) ......................................................................... (Eq. 8.9)

where

M* @ = strength reduction factor kl , k4, k8 k6, k24 Z

fb = characteristic bending stress a = slope of the upper surface of the beam.

= the design bending moment

= modification factors as given in section 2 = modification factors as given in section 8.7 for bending = section modulus of the beam (for rectangular beams, 2 = bd2/6 where bequals

the breadth and d equals the depth of the beam).

8.8.3 Tapered beams (see figures 8.2(a) & (b)) For single or symmetrical double tapered beams carrying a uniformly distributed load, Wthe criiical stresses shall be determined at the tapered edge at the section of depth, d where

....................................................................... (Eq. 8.10)

with de and dc

= minimum beam depth = depth of beam at mid-span.

The location of the section is given by

(Eq. 8.11) .......................................................................



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S N Z NZS*3b03 9 3 = 8583169 0010878 2TO

NZS 3603: 1 993

Stresses shall be determined from

av =ax tana

(Eq. 8.12) .......................................................................

....................................................................... (Eq. 8.13)

(Eq. 8.14) 2 cry =ax tan a

The following shall be satisfied

.......................................................................

(Eq. 8.15) .......................................................................

where

Fb FP FP Fs 9 ki , k4, k8 k24 fb

‘p fS

=Y ow

OX

C8.8.3

= 9kl k4k6k8k24fb = dkl k4fp when the tapered edge is in compression = 0.33 Fs when the tapered edge is in tension

= strength reduction factor = modification factors as given in section 2 = modification factor as given in 8.7 = characteristic bending stress = Characteristic bearing stress perpendicular to the grain = characteristic shear stress = longitudinal stress for tapered beams = transverse stress for tapered beams = shear stress for tapered beams

= M k 4 f S

For the analysis leading to the above requirements see US Department of Agriculture Report FPL 34. A practical example is detailed in the American Institute of Timber Construction Manual. In a tapered beam a component of stress perpendicular to the grain will exist at the sawn tapered surface. This will be tensile or compressive corresponding with the principal bending stress in that surface. Where possible the sawn edge should be in compression .

96



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SNZ N Z S * 3 6 0 3 9 3 W 8583367 O030879 137

NZS 3603: 1 993

L I I A A

1 I

r (a) Single tapered-straight

-1

A A

(b) Double tapered-straight

A

I A

I I I I

I - - 1 (cl Double tapered-pitched (tangent ends)

I. I L 1

4 Id) Double tapered-curved (constant curvature)

Figure 8.2 - Simple span tapered beams

8.9 Butt joints

8.9.1 Butt joints shall not be used in the curved portions of curved members.



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SNZ NZSa3603 9 3 8583169 OOl10880 959 W

NZS 3603: 1 993

8.9.2 The interaction of tensile stress, at and shear stress, as at a butt joint (computed on the gross cross section using linear elastic theory and strength limit state design actions) shall comply with:

(a) In tension members and horizontally laminated beams:

(i) For outermost laminations -

....................................................................... (Eq. 8.16)

(i¡) For inner laminations -

+ 21.0 (Eq.8.17) o,t,0*5 ....................................................................... 15Fsk29 1.7Fsk29

(b) In vertically laminated beams:

(i) For outermost laminations -

(i) For inner laminations -

51.0 0tte0a5 30Fska

where

....................................................................... (Eq. 8.18)

....................................................................... (Eq. 8.19)

te = lamination thickness

$ = strength reduction factor kl /ql &, = modification factors as given in section 2 k29 = modification factor as given in 8.9.3 at = tensile stress at a butt joint US = shear stress at a butt joint

FS = $klk4k5fs

8.9.3 The value of the factor k29 shall be 1 .OO, when there are not more than four butt joints located in zones of maximum stress. The zone of maximum stress is defined as that zone where the tensile stress is greater than 0.8 at.

Where the number, n of butt joints in zones of maximum stress is five or more then

1.3 k29 = n0.2 ... ..................................................................... (Eq. 8.20)

C8.9.3 Most manufacturers of glue laminated timber have facilities for the manufacture of high strength enàpints and in general it is not economr'cat and to specify butt joints because of the manufacturing difficulfies they cause in moderate length members. They may prove e c o n o m ~ l and in exceptionally long members with thin laminations.

98



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S N Z NZSm3603 9 3 8583169 001088L 895

NZS 3603: 1 993

8.10 Camber Camber may be built into members to compensate for deflection and creep under long-term load i ng .

c8.10 In simply supported beams, a camber of 1.5 times the deflection due to long-term bad (thaì is, dead load plus effectively permanent superimposed bad) should reSufi in a level Sofffi.

8.11 Holes drilled in fabricated members The effects of drilled holes shall be allowed for in design.

c8.11 The effect of bolt holes should be considered by using net section properties for design purposes. Nail holes are generally Considered to have no effect on the strength of timber members. However, recent testing suggests that the flexural strength of glue laminated timber may be reduced by large concentrations of nails in regions of high stress.

8.12 Nail plate joints The nail pattern at moment resisting nail plate joints shall be designed such that the nails do not cause significant stress concentrations in the glue-laminated timber members.

a. 12 Stress concentrations are reduced where the nails are spread over a reasonably large proportion of the joint area and there is not a large number of nails in any one lamination.

Stress concentrations are also reduced if there are no nails in the outermost lamination.

Where possible, wood qualify in highly stressed outer laminations should be controlled to avoid finger joints and wood that only just meets the requirements of the specified grade.

99



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SNZ N Z S t 3 6 0 3 73 8583369 0030882 721

NZS 3603: 1 993

9 DESIGN FOR FIRE RESISTANCE

9.1 Scope This section sets out methods for calculating the fire resistance of load bearing structural timber members.

9.2 Fire resistance ratings Fire resistance ratings for load bearing timber elements or assemblies shall be established by:

(a) Standard fire tests in accordance with AS 1530 Part 4 or other approved standard, or

(b) Extrapolation from standard tests using well established criteria, or

(c) Calculation in accordance with design criteria set oui in this document, or

(d) Determination of the time taken to the start of charring of the load bearing timber elements when shielded by appropriate materials and subjected to the thermal environment of the standard fire test.

C9.2 Clause 9.2(b) permits extrapolatîon of the results of standard tests. For tests of Ibht timber frame assemblies, the test results may be applied to similar systems where the stud orjoist size is not less than those tested, the spacings are not greater than those tested, and the stresses in the structural elements are not greater than those tested. BRAN2 Technical Recommendation TR9 may be used for walls or floors with larger dimensions or h d s than those tested,

Clause 9.2(d) provides a means of determining fire resistance ratings for load bearing timber elements tested in an unloadedcondition in the standard fire test. It is particularly suited to smallsecticm membersin combination with gypsum plaster board iinings, for example, timber stud walls and timber joist floors. It is assumed that in the period until the onset of charring of the timbeq collZpse wouldnot occur even if the element was fullyioaded, Themethoddoes not cuver the performance of fastenings atpresent but evidence may be submitted to show that fastenings can be protected simi/arly.

Where elements are also required to contain a fire, for example, floors and walls, they must also meet the insulation and integrity requirements of the standard test,

9.3 Loads Load combinations for fire design are given in NZS 4203.

9.4 Calculation of fire resistance rating of timber elements

9.4.1 Assessment of FRR The fire resistance rating of a timber element may be assessed by assuming that charring of the exposed surfaces of the member occurs at a uniform rate. The residual section shall be such that the member will support the loads set out in 9.3 without exceeding the design strengths given in 9.4.3.

C9.4. f Thermal breakdown of timber When exposed to the heat of a fire, timber undergoes a thermal breakdown @yrolysis) into combustible and non-combustible gases, and a hyer of charcoal forms on the burning surface. The rafe of progress of the pyrolysis is governed by the low the& conductivity of the timber and the lower coductjviîy of the charred layer, which also hiders the access of oxygen to the timber surface. The total insulating effect of the char and timber is such that temperatures only a short distance in from the char line will not rise sufficiently to impari the strength of the w d . The decrease in load carrying capacity of a timber member exposed to fire will &e a functh of the reduction in cross sectional area of the member. Small timber members have negligible fire resistance, but as cmss section dimensions increase, fire msìstance also increases.

1 O0



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S N Z NZS*3603 93 8583369 OOL0883 668

NZS 3603: 1993

9.4.2 Charring rate Thecharring rate of radiata pine and other timber species of approximately the same density shall be taken as 0.65 mm per minute. The charring rate of species with significantly greater density may be established by test or by calculation in accordance with BRANZ Study Report No. 42, 1992.

c9.4.2 Fire retardant treated timber Fire retardant treatment is ofgreat value forreducing the rafe of flame spread on the surface of timber. However, even if fíaming is duced, a retardant cannot render the timber immune from structural damage by destructive distillation under the heat of burning building contenîs. There has been little tesí work done on retardant-treated heavy timber constructbn, but the present inàication is that treatment has no measurable effect on the total fim resistance of large section members. For caiculatmn purposes retardant-treated timber should be assumedto have the same charring rate as untreated timber, unless tests from a rec6gtl¡Sed fire test laboratoiy are supplièd.

9.4.3 Design strength For the purposes of fire resistance rating calculations the design strength shall be calculated using a k1 factor of 1 .O (for brief duration loads) and a strength reduction factor, Ø= 1 .O, in addition to any other appropriate modification factors.

9.4.4 Residual cross section The residual crosssection of a structural element shall be assessed by deducting from the original cross section dimensions a thickness of material equal to a rate of charring multiplied by the fire resistance rating period in minutes. The deduction shall be made from each surface exposed to the fire. Allowance shall be made for accelerated charring at exposed arrises by assuming that the radius of rounding of the arris equals the calculated depth of charring (see figure 9.1).

I . . p . y s e c t i o n - Calculated depth of charring

Profile of original section

Radius of arris rounding

The radius of arris rounding, r,equals the calculated depth of charring.

The area of the section lost due to rounding will be

and the centre of gravity of thls area will lie at a distance from either side of

A =0,215 i*

y -0.223

Figure 9.1 - Radius of arris rounding

1 o1 Copyright Standards New Zealand Provided by IHS under license with SNZ Licensee=Unitec Inst of Technology/5911177001


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SNZ NZSS3603 9 3 = ô583369 0030884 5 T 4

NZS 3603: 1 993 ~~

9.4.5 Minimum sizes The design method described above shall not be used for beams or columns less than 90 mm in any dimension.

9.5 Details of construction

9.5.1 Joints The charring rates given in 9.4.2 shall apply to all exposed surfaces including butting timber-to- timber surfaces that are not held in close contact and timber surfaces in contact with or adjacent to unprotected metal items.

C9.5. I Metal fasteners where any pari of a metal fastener becomes exposed to heat during a fire, rapid heat conduction will lead to lacalised charring with possible loss of anchorage. Where this effect is likely to lead to the failure ofa structural member which is required to have fire resistance, protection of the fastener should be provided:

(a) By embedment of the fastener so that all parts of the metal remain within the residual section. Any countersunk holes should be plugged with timber glued in position; ur

(b) By covering the fastener with a suitable protecting material, for example, timber, plastehoad, or equivalent;

Special affentbn should be paid to the fixing of protective materials to ensure that they will remain in position for the required period of fire resistance.

9.5.2 Glues Glue laminated timber members, glued with thermo-setting synthetic resins such as urea formaldehyde, resorcinol formaldehyde, phenol formaldehyde, melamine formaldehyde or mixtures of these may be considered to resist fire attack in an equal manner to solid timber.

9.5.3 Gaps in members Members with gaps, or members with parallel laminations nailed or bolted together shall not be treated as one section but shall have the fire resistance rating assessed by considering that the fire may reach all faces of each lamination.

c9.5.3 Structures should be detailed to achieve solid masses with smooth surfaces and members close fitting to avoid cracks, gaps or concealed spaces likely to have a flue action during a fire. Thin sections and sharp projections should be avoided. Abutting surfaces can be painted with intumescent paint to reduce the likelihood of fire penetration.

9.5.4 Solid f h t s The fire resistanceof asolid timber floorshall becalculated by assuming lossoftimber by charring from the underside of the floor only. Vertical joints between planks shall be sealed to prevent direct passage of the fire from floor to floor. Where a timber tongue and groove joint seal is used the thickness of the tongue shall be 1.1. times the thickness of char calculated for the particular fire resistance rating period.

9.5.5 Beams The charring shall be subtracted from all faces of beams except those areas protected by a floor of equal or greater fire resistance. The slenderness coefficient for lateral buckling shall be calculated using 3.2.5.2, considering the size of the residual cross section and the fire resistance of those members intended to provide lateral restraint.

102



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SNZ N Z S * 3 b 0 3 9 3 = 8583367 0030885 430 NZS 3603: 1 993

c9.5.5 The section modulus, Z, , of a charred beam can be calculated as fol10 ws:

Four sided chatring:

2, = -[(b- 1 2tc)(d - 2tC)* - 2.58tc2(d- 2tc)]

Z, = --(d 1 - 2tc)[(b - 2tc )(d - 2tc) - 2.58tc2]

................................................... (Eq. 9.1) 6

or

(Eq. 9.2) .....................................................

Three sided chambg:

2, = -[(b- 1 2tC)(d-2tc)' -t29fc2(d - tc ) ] ..................................................... (Eq. 9.3) 6

or

(Eq. 9.4) Z, =-(d 1 - tc)[(b- 2tc)(d - tc)-1.92tc2] .......................................................... 6

where

b = breadthofbeam d = depthofbeam tc = thickness of charring

9.5.6 Columns The charring shall be subtracted from all surfaces of a column except those protected by a wall of equal or greater fire resistance in close contact with the column.

The relationship between cross section dimensions of the charred section and fire resistance is dependent on stress, slenderness and end restraint. Calculations shall be made for each particular case.

No rotational restraint in direction at the ends (as distinct from positional restraint) shall be assumed in determining the effective length of the residual column unless it can be shown that such restraint exists.



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SNZ NZS*3603 93 W 8583369 003088b 377

10 TESTING OF TIMBER STRUCTURES

10.1 General

10.1.1 Application The testing of full-size timber structures or parts of structures (called units in this section) may be carried out to demonstrate compliance with this Standard. The test arrangement shall represent as closely as possible the proposed structure or part of the structure.

This section shall not apply to the following circumstances:

(a) The determination of characteristic stresses or strengths;

(b) The grading of timber;

(c) The quality control of production processes;

(d) The testing of structural scale models.

10.1.2 Type of test The testing shall take the form of

(a) Prototype or sample testing complying with 10.6, or

(b) Proof testing complying with 10.7.

ClO. 7.2 Prototype resting is the testing of one or more units to ascertain the structural adequacy of units that are tobe manufactured nornina//y equalorbetter than those tested. Sample testhg is the testing of a sample of units randomly selected from an existngsef of units. Proof testing is the testing of any one unfi to determine the structural adequacy of that unk

10.1.3 Agreement on acceptance criteria Before testing commences, the parties concerned shall agree upon the load values, strengths and stiffness criteria, RA (see 10.4.7) and any other relevant criteria.

10.2 Testing authority The testing of units shall be carried out by an agency agreed by the parties concerned.

c10.2 An example of the "agemy" would be a !&oratory registered by the Testhg Laboratory Registration Council (Telarc) for the partkular tests concerned or a Design Engineer.

10.3 Testing conditions

C10.3 Albwance should be made for eflecfs of misture content, duration of M i n g , symmetry of loading, support from adjacent units or members, eccentricity of suppotis, and eccentric* of load application if these differ significantly from actual senke condithns.

10.3.1 The actual service conditions shall be simulated as closely as possible in both the application of test loads and the support of the units tested.

10.3.2 Where service conditions cannot be simulated then allowance shall be made to compensate for the expected effects.

104



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SNZ NZSN(3b03 93 M 85831b9 O010887 203 M

NZS 3603: 1 993

10.4 Test procedure

10.4.1 The test load shall be calculated in accordance with 10.6 or 10.7 as appropriate.

10.4.2 Each unit shall be preloaded. Preloading shall consist of applying to the unit a load equal to the long term serviceability design load for a period of 5 min, after which time it shall be removed.

10.4.3 A load-deflection trace shall be plotted during each test on each unit. The load-deflection trace need not be obtained during the preloading unless specifically requested by one of the parties concerned.

C10.4.3 The load-deflection trace will serve not only as a checkagainst observationat errors but also to inúkate any irregularities in the unit’s behavbur under load and fo enabfe a particular weakness to be investigated as the test progresses. It is desirable that a minimum of six points, not including the zero loadpolnt, be obtained to define the shape of theload-deflection trace if it is predominantly linear, and a minimum of 7 U points if it is significantîy non-linear.

10.4.4 The rate of application of the load shall be decided upon by all parties concerned.

10.4.5 The unit shall be loaded up to the stiff ness test load (TíA) and the deflection at this load shall be recorded. The load shall be removed at the same rate as it was applied until no load is acting. The deflection shall be recorded in the no load state. The load shall then be applied until the load has reached the strength test load (TLB). The deflection shall then be recorded. The load shall be removed at the same rate as it was applied until no load is acting. The deflection at zero load shall be recorded.

10.4.6 Any unexpected behaviour occurring to any unit during the test shall be recorded.

10.4.7 The ratio, RA shall be computed as follows:

....................................................... Eq. 10.1) Irrecoverable deflection due to load TLA Deflection under load T U

RA =

where RA is an appropriate value for the units concerned.

C10.4.7 Appropriate values of RA depend on the type of units and on the dkectiorrs of the dead and superimposed loads, and COUM be as follows:

Type of structure RA

Beams, solid or glulam Po&¡ frames, glued joints Shear walls, glued panei materials

Portal frames, mechanically fastened Trusses, nail plate fasteners

Shear walls, mechanically fastened Floor diaphragms, panel materials, nailed

o, O5

io, 10

0.20

1 05 Copyright Standards New Zealand Provided by IHS under license with SNZ Licensee=Unitec Inst of Technology/5911177001


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NZS 3603: 1 993

10.5 Acceptance criteria

10.5.1 Acceptance for stiffness The unit shall pass the stiffness test if the following criteria (a) and (b) are satisfied:

(a) RA is less than or equal to the agreed value

is in accordance with the agreed T U deflection at load TL4

(b) The stiffness given by the ratio,

criteria.

10.5.2 Acceptance for strength The unit shall pass the strength test if the test load TL5 is attained and, for the case of proof testing, no unacceptable permanent damage occurs during testing.

10.6 Prototype or sample testing

10.6.1 General

10.6.1.1 The number of units to be tested, the method of ensuring that prototypes are representative of probable production, and the method of random selection from the total population shall be agreed by all parties concerned.

10.6.1.2 If any one unit fails to meet the acceptance criteria for strength or stiffness then the test has not been passed. The total population that the units represent is deemed to be unacceptable.

C10.6. I Further testing of additional units may show that the population is acceptable because kj 9 reduces as the sample size increases. Alternatively, proof testing could be used to determine the acceptable members of th8 population.

10.6.2 Test loads

(a) The stiffness test load (TíA) shall be the most critical serviceability limit state load given in the relevant sections of NZS 4203.

(b) The strength test load (TLB) shall be:

U TL5 = k3ok31ksz - ..................................................................................................... Eq. 10.2) kl

where U = the most critical ultimate limit state load given in NZS 4203 kl = load duration factor as given in table 2.4 and as used in the design b o = as given in table 10.1 kl = as given in table 10.2 k32 = as given in table 10.3.

C10.6.2 All likely combinations of permanent loads and imposed loads of short duration, including those due to wind, earthquake and, where applicable, those due to impact, shallbe taken into account when determining the worst loading conditions. The value of k l should be that value associated with the briefest load in the most critkal combination of loads. k31 is a facfor to compensate for the time to reach test load being greater than 15 minutes. The coeffkient of variation associated with the sampling factor k32is chosen on the basis of experience already



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SNZ N Z S * 3 6 0 3 93 8583169 O010889 O86

NZS 3603: 1993

Time to reach TLB 15 min 30 min

k3 1 1 .o0 0.98

gained with similar types of structures as those being tested. The coefficient of variation refers to the overall performance of the parent population from whkh the fest units were taken.

l h 2 h 6 h

0.96 0.93 0.90

Table 10.1 - Compensation factor, í ~ o

Structure or structural element

Beams with slenderness coefficients greater than 1 O, and all columns:

Timber initially dry Timber initially green

Metal connectors:

Failure in timber that is initially green For failure of metal

For all other

..

k 0

1.1 1.4

1.2 kl /k3 1

1 .o

Table 10.3 - Sampling factor, ir372

Sample size

n

1 2 3 4 5 7

10 14

>19

Likely coefficient of variation (see table 10.4)

0.10 0.15 0.20 0.25 0.30 0.35 0.40

1.27 1.45 1.20 1.33 1.16 1.26 1.14 1.22 1.12 1.18 1 .o9 1.13 1 .O5 1 .O8 1 .O3 1 .O4 1 .o0 1 .o0

10.7 Proof testing

1.66 1.91 2.21 1.47 1.64 1.83 1.37 1.50 1.64 1.31 1.41 1.52 1.26 1.34 1.43 1.19 1.25 1.31 1.12 1.15 1.19 1 .O5 1.07 1.09 1 .o0 1.00 1.00

2.56 2.98 2.05 2.31 1.80 1.98 1.65 1.78 1.53 1.64 1.38 1.45 1.23 1.27 1.10 1.12 1 .o0 1 .o0

C10.7 In the case of proof testing only those units that carry the agreed test loads and meet the agreed stiffness criteria are deemed to be acceptable.



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SNZ NZS*3603 73 8583167 0010890 B T 8

Structure or element

Framing timber - Bending strength Tensile strength Compression strength (as short column)

Finger-jointed elements - Bending strength

Connections - Nailed joints Toothed plate and other mechanical fasteners

NZS 3603: 1 993

Likely range of coefficients of variation of strengths of individual units

0.20 - 0.35 0.30 - 0.45

0.15 - 0.20

0.15 - 0.20

0.15

0.10 - 0.15

10.7.1 Test loads The critical combination of design loads shall be determined by the person responsible for the design, as follows:

(a) The stiffness test load (TLA) shall be the most criflical serviceability limit state load given in the relevant sections of NZS 4203.

(b) The strength test load (TLB) shall be:

U nB= kmk31K ........................................................................ Eq. 10.3)

NOTE - It should be appreciated that where the population of a particular type of unit is continuously increasing, quality control tests will gradually build up an adequate sample andthus provide the most reliable value for the coefficient of variation. Where the population is very limited, that is, only a few units of the particulartype are to be manufactured or constructed, it would generally be more economical, and certainly provide more reliable information as to their probable service performance, if each one of the units were to be proof-tested rather than one or two being selected as prototype and tested as such.

10.8 Reporting of tests The testing authoriiy shall prepare a report of the test on each unit, which shall include clear statements on:

(a) The conditions of testing, including the method of loading, the method of measuring deflection, the agreed strength and stiffness criteria and any other relevant data.

(b) The average moisture content of the timber of the tested unit at the tirne of assembly.

(c) The nature and size of defects in the timber, especially at the point of failure, if failure occurs.

(d) The test results.

(e) Whether or not each unit satisfied the strength and stiffness criteria agreed upon by all parties concerned.

(f) The average density of the timber at time of test of each unit tested, provided that density measurements are feasible.

(9) The loading required to be sustained by the structure or structural element as supplied by the person responsible for the design and in accordance with NZS 4203.

108



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SNZ NZS*3b03 93 85831b9 OOLO891 7 3 4

NZS 3603: 1993

APPENDM A THE DETERMINATION OF CHARACTERISTIC STRENGTHS FOR METAL FASTENERS FOR TIMBER

A l General Characteristicstrengîhsfor metal fasteners in timber shall be determined by the requirementsset out in AS 1649 as modified by A2 and A3.

A2 Modifications to AS 1649

(a) Joints shall be assembled wet (moisture content greater than 30 %) and tested dry (moisture content 16 I2 %), except that joints may be assembled dry and tested dry, or assembled wet and tested wet, provided that the chosen moisture conditions are representative of those in the timber during its expected use.

(b) Fasteners that are intended for use under a loading condition other than that provided for in AS 1649 shall be tested in such a manner as to represent that loading condition.

(c) For category C fasteners tests shall be arranged to;

(i) Induce maximum effects in the plate-timber connection,

(i¡) Induce maximum effects in the plate.

(d) Characteristic strengths shall be calculated as the 5 percentile load based on a log-normal distribution. The formulae for calculating characteristic strengths become:

Withdrawal loads:

N/mm LPL (30 x 1.5)

For nails

N/mm LPL (15 x 2.0)

For screws

Lateral loads: Category A fasteners LPL2 /2

Category C fasteners LPL2 /ne Category D fasteners LPL2 /ne

N

N N

Category B fasteners LPU2 N

where ne = number of single shear units acting in the joint

Values of klisted in clause B4 of Appendix B of AS 1649 shall be replaced by the following:

Number of test results

n 10 11 12 14 16 18 22 26 30

k 1.92 1.89 1.87 1.83 1.81 1.79 1.76 1.74 1.73

A3 Density adjustment The characteristic strengths determined by the procedures set out in section 6.0 of AS1 649 shall be modified to represent the characteristic strength for the fastener when applied to a timber

~~

1 o9



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~ ~

SNZ N Z S x 3 b 0 3 9 3 8583369 0030892 670

NZS 3603: 1 993

having an average density equal to the reference density for that timber. The reference density for radiata pine and Douglas fir shall be as set oui below:

Density type Moisture kg/m3 content %

Radiata pine

Douglas fir

Basic Nominal Nominal Nominal Test Test Test Oven dry

- 12 16 20 12 16 20 O

41 O 434 428 423 486 497 508 452

400 430 423 416 481 49 1 500 452

where

Basic density = oven dry weightkolurne when green Nominal density = oven dry weightívolume at nominated misture content Test density

Oven dry density = oven dry weighüoven dry volume

= weight at nominated moisture contentholume at nominated moisture content

Therefore:

Characteristic strength at test x (Reference density) (Average test density)

Characteristic strength =

110



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SNZ NZSw3b03 9 3 85833b9 0030893 507

NZS 3603: 1993

APPENDIX B LATERAL AND TORSIONAL BUCKLING RESTRAINTS

61 General

B1.l The following method may be used for a design of slender beams having equally spaced buckling restraints. The restraint systems considered are either lateral or torsional ones as shown in figure B1, where the restraint stiffness KA and Ks are defined as follows:

................................................................................... FA = KAAA (Eq. Bl )

................................................................................... TB = KBBB (Eq. 82)

where FA and Ts are the restraint force and torque respectively that occur when the point of attachment of the restraint to the beam undergoes a displacement AA and rotation BB . It is assumed that the ends of beams are effectively restrained against torsional rotation (see C2.1).

B I .2 Notation Notation to be used in the design formulae is defined as follows:

4 3 = 1 .O when loads are live loads only = =

1.5 when loads are dead loads only and timber is initially dry 2.0 when loads are dead loads only and timber is initially green.

Note that values of k33 for other conditions may be obtained by linear interpolation.

k34 = 1 .O for sawn timber members = 0.4 for laminated and other carefully fabricated timber members

m + 1 2

k35 = lesserof - and 5

rn = number of members supported by each restraint system nr = number of equally spaced intermediate restraints Sm, = Smjn. =

slenderness coefficient if there are no restraints slenderness coefficient if the restraints are effectively rigid.

(a) Column lateral restraint

Y

(b) Beam lateral restraint

Y

(c) Beam torsional restraint

Figure B1 - Intermediate restraints

111



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SNZ N Z S * 3 6 0 3 73 8583169 0010894 4 4 3

NZS 3603: 1 993

82 Columns

62.1 Load capacity

In computing the load capacity of a column of length, L with nf intermediate lateral restraints as shown in figure B1 (a), the slenderness coefficient, S3 may be taken as:

sma. s -- 3 - 0.25 al

..< ....................................................................... (Eq. 83)

but not less than Smjn. and not more than Sm,, and where:

......................................................................... (Eq. 84)

62.2 Force on lateral restraints The design force FA on the lateral restraints of a column subjected to an axial load PA may be taken as

......................................................................... (Eq. B5)

B3 Beam with lateral restraints

63.1 Load capacity In Computing the load capacity of a beam of length, L with nf intermediate lateral restraints as shown in figure Bl(b), the slenderness coefficient, S1 may be taken as:

....... ..... .............. ................................................ , (Eq- B6)

but not less than Smjn. and not more than Sma., where

....................................................................... (Eq. B7)

83.2 Force on lateral restraints The force, FA, on each lateral restraint of beam subjected to a bending moment, MA may be taken as

........................................................................ (Eq. B8)

for members of rectangular section and for box beams, or

O. 1MA d(n, + 1)

FA = k33 k34 k35

for I-beams

......................................................................... (Eq. B9)



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~~

SNZ NZSx3b03 93 W 8583169 0010895 38T m

NZS 3603: 1 993

84 Beam with torsional restraints

B4.1 Load capacity In computing the load capacity of a beam of length, L with nrintermediate torsional restraints as shown in figure B1 (c), the slenderness coefficient, SI may be taken as:

s, = %ax* (1 + a3)0.25

...................................................................... (Eq. B10)

but not less than Smin. and not greater than S,, and where

....................................................................... (Eq. B11)

B4.2 Torque on torsional restraints The torque Tgon each restraint of a beam subjected to a bending moment MA may be taken as

O. 4 MA TB = k33k34k35 (Eq. 812) .......................................................................

for members of rectangular section and for box beams, or

0.15M~ (n, + 1)

TB = k33k34k35

for I-beams.

....................................................................... (Eq. 813)



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S N Z NZS*3603 9 3 8583L69 0030896 2Lb

NZS 3603:1993

APPENDIX C SLENDERNESS COEFFICIENTS FOR BEAMS

C1 General

c1 .I To evaluate the stability factor k8 of 2.10 the slenderness coefficient of a beam shall be defined by:

0.5

......................................................................... (Eq. Cl)

where ( ~ 1 ) ~ is the stiffness in bending about the XX axis, ythe distance from the neutral axis to the extreme fibre, and &the Euler buckling moment of the beam.

NOTE- In some odd cases, the evaluation of the aboveformulafor asolid beam of rectangular section, can lead to avalue of S1 greaterthan given bythe formula in 3.2.5.2. In such acase, the value as given by3.2.5.2 may be used for obtaining ka.

c1.2 The evaluation of the slenderness coefficient requires a knowledge of ME, the Euler buckling moment. Values of the Euler moment for particular structural situations can be obtained from standard texts on structural analysis. However, as an aid to design, some values of the Euler moment are presented in the following clauses.

C2 End-supported beams

C2.1 General The following recommendations are applicable to end-supported beams of bisymmetrical cross section for which the contribution of warping stiffness to the buckling strength may be neglected.

The ends of supports are assumed to be effectively restrained against twisting. This condition will be satisfied if the supports possess a torsional stiffness in excess of 20(GJ)lL, where GJis the torsional stiffness of the beam and L is its length. For rectangular sections:

......................................................................... (Eq. C2) J = 1 - 2 - ( "d")"B A useful reference for information on more general sections, including the effects of warping stiff ness, is the following:

NETHERCOT, D.A., and ROCKEY, K.C. 'A Unified Approach to the Elastic Lateral Buckling of Beams', The Structural Engineer, Vol. 49, No. 7, July 1971, pp 321-330. (For erratum see Vol. 51, No. 4, April 1973, pp 138-139.)

C2.2 Beams with intermediate buckling restraints

The Euler value of the maximum moment between two buckling restraints may be taken as:

... ........................................................................ (Eq. C3)

114



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~

SNZ N Z S + 3 b 0 3 9 3 = 8583169 0010897 152 =

NZS 3603:1993

where

(E& (€i),, = effective stiffness for bending about the major and minor axes respectively GJ = effective torsional stiffness

a

= constant obtained from table C1 = distance between buckling restraints.

cs Lay

For rectangular sections of solid wood, a consetvative approximation to thevalue of slenderness coefficient obtained from formulae (Cl) and (C3) is:

0.5

(Eq. C4) ........................................................................

Table C1 - Coefficients for slenderness factor of bisymmetrical beams with intermediate buckling restraints

Slenderness factor C5

Fixed Moment parameter

(see diagram below) restraint restraint b

condition condition

1 .o 0.5 0.0 -0.5 -1 .o

3.1 4.1 5.5 7.3 8.0

6.3 8.2 11.1 14.0 14.0

NOTE - In tables C1 and C2, the values of the coeff icients Qj and CG apply to beams with lateral restraints only at their end joints. However, these coefficients may be used for any other beam load system that has a similar shape of bending moment diagram between points of lateral restraint.

Intermediate buckling

/ restraints \ I

Y (al Side elevation of beam

(b) Diagram of bending moment between buckling restraints

The buckling restraints must prevent rotation of the beam about the U axis. The terms ‘free’ and ‘fixed restraint conditions refer to the possibility for rotation of the beam about the YY axis at the restraint locations.



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SNZ NZS+3b03 93 8583369 0030898 O99

NZS 3603: 1 993

C2.3 Beams with 170 intermediate buckling restraints For this case the Euler value of maximum moment may be taken as:

.................................................. aGJ

where

h Cg. Q = constants obtained from table C2 Lay = L = spanofbeam.

= height above centroid of the point of load application

For beam loaded only by end moments, formula (C5) may be used with C, = h = O and the coefficient Q taken from table C1.

For rectangular cross sections of solid wood, a conservative approximation of the value of slenderness coefficient obtained from fomulae (Cl) and (C5) is:

s, =

dLay 4.8- b2 ......................................................................... (Eq. C6)

Formulae (C4) and (C6) are good approximations when b 5 O. 5d.

C3 Continuously restrained beams For beam of bisymmetrical cross section, continuously restrained against lateral displacement at a distance, yo below the neutral axis (see figure Cl), the Euler moment, MEmay be taken as:

Neu trai axis

Figure C I - Continuously restrained beam



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~~ ~~

SNZ NZS*<3603 93 8583369 0030899 T25 W

NZS 3603: 1 993

Table C2 - Coefficients for slenderness factors of bisymmetrical beams with no intermediate buckling restraints

Slenderness factors

Conditi of end restrair againsl rotatioi about Y ï axis

Free Fixed

Bending moment M

Load in g c5 C6

3.6 6.1

1.4 1.8

Free Fixed

4.1 5.4

4.9 5.2

Free Fixed

4.2 6.7

1.7 2.6

Free Fixed

4.5 5.3

5.3 6.5

Free Fixed

1.3 -

3.3 -

Fixed 4.0 2.0

2.0

,

Fixed 6.4

See diagram in table C1 (free ends of cantilevers excepted).

NOTE - In table C2, the values of the coefficients C5 and 6 apply to beams with lateral restraints only at their end joints. However, these coeff icients may be used for any other beam load system that has a similar shape of bending moment diagram between points of lateral restraint.

117



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SNZ NZS*3603 93 W 8583169 0010700 577

NZS 3603:1993

APPENDIX D SLENDERNESS COEFFICIENTS FOR COLUMNS

D I To evaluate the stability factor of 2.10, the slenderness coefficient of a column shall be denoted by &for bending about the major axisonly and S3for bending about the minor axisonly. The value of the slenderness coefficient shall be obtained from

........................................................... (Eq. DA)

where (EA) is the effective stiffness under axial loading, and PEis the Euler buckling load of the column.

For pole timbers, the effective column cross-section may be taken as equal to the cross section at a location 0.4 La from the smaller end of an unrestrained portion of a column.

For a bisymmetrical column, continuously restrained against lateral displacement at a distance yofrom the neutral axis (see figure Dl), the slenderness coefficient with respect to lateral buckling may be obtained from the following formulae:

0.823(€A) s3=[ PE ] ..................................................................... (Eq. D2)

where

(EA 1 = effective axial stiffness (U) , , (GJ 1 = effective torsional stiffness

= effective bending stiffness about major and minor axes

Neutral axis

Figure D I - Continuously restrained column

118



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~~

S N Z N Z S x 3 6 0 3 93 m 8583169 0010701 403 m

NZS 3603:1993

APPENDIX E DEFORMATION AND DISPLACEMENTMODULUSOFMECHANICALLY FASTENED JOINTS

E I Where specific test information is not available for the stiffness of the joints to be used in the structure, the displacement between abutting faces of the two members secured by mechanical fasteners may be estimated from the following formula:

......................................................................... (Eq. E l ) P 6 = 6, + 6, = K

where

Sp = displacement due to load P (mm) 61 = initial slip in joint (mm) K = displacement modulus (N/mm)

The following values of Kand 61 give reasonable approximations to displacements occurring in mechanically fastened joints with due regard to the effect of duration of load and repeated applications of live loads:

For bolts, split-rings connectors and shear plates -

......................................................................... (Eq. E21

Qck and P being in newtons

61 = o for a load superimposed on an existing load,

for bolted joints with holes drilled 1.5 mm oversize, 3 - - ~ ~ 0 . 5

for split-ring connectors or shear plates. 1 - - 2,,0,5

where

n = number of fasteners sharing load k36 = 0.85 for unseasoned timber

= 1 .O0 for seasoned timber

Values of k37 are given in table E l .



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SNZ NZS*3603

Duration of load

More than 6 months 2 weeks - 6 months 5 minutes - 2 weeks less than 5 minutes

NZS 3603: 1 993

Nails

Unseasoned Seasoned members members

10 5 3 2 1.5 1.5 1 1

93

Unseasoned members

W 8583167

Seasoned members

0010902

4 2 1.5

3 4 T

3 2 1.5

Table E l - Duration of load factor, k37

I Factor, k37

Bolts, split-rings and shear plates

120



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SNZ NZS+3b03 9 3 m 8583169 OOLO903 286 m

NZS 3603: 1 993

APPENDIX F METHOD OF COMPUTING EFFECTIVE SECTION PROPERTIES OF PLYWOOD

CF The method in this Appendix is baseci on standard engineerîng elastk bending theory for layered materials using a transformedarea approach. Any similar method may be used. The alternative methods given in AS 2269/NZS 3614 are similar but do not include section prqoerties for shear.

For plyw~od stressed perpendicular to the face grain factors, k75 and k16 may be used instead of calculated section properties.

F1 Figure F1 (a) depicts a cross section of 7-ply plywood, but the same method can be used for plywood with any (odd) number of plies. Assuming that it is symmetrical in respect of both the thickness and the elastic moduli of corresponding veneers on opposite sides of the central axis, that is that the neutral axis lies in the central plane, the effective values of area, moment of inertia, section modulus, and first moment of area of the section may be computed as set out in F2 and F4.

Parallel plies

Perpendicular

x1= t 1 la) Typical plywood cross section

(7-ply shown, notation to be adjusted appropriately for other assemblies)

End grain

Side grain

(b) Plywood face grain

Figure F1 - Dimensions and nomenclature used in Appendix F

121



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~~

SNZ N Z S J 3 6 0 3 9 3 8583369 0030904 3 3 2

NZS 3603:1993

F2 The actual properties of the “parallel plies”, that is, plies whose grain is parallel to the face grain, and “perpendicular plies”, that is, plies whose grain is perpendicularto the face grain, areobtained separately. Thus, for a strip of unit width:

Area

Parallel plies AL = ( X I - x2 + ~3 - ~ 4 )

Perpendicular plies A, = (x2 -x3 +x4)

Moment of inertia

Parallel plies IL = 0.083 (x l3 - xz3 + ~ 3 ’ - ~4~ )

Perpendicular plies 1, = 0.083 (xg3 - ~3~ + ~4~ )

First moment of area

Only the material lying outside the critical plane for rolling shear in a panel acting as a beam is considered for first moment of area.

In this Appendix the critical plane is assumed to be the central veneer in all cases (but see figure 6.2). Consequently the expressionsfor QL and 0 1 are slightly in error for 5-ply and 9-ply panels, and the expressions for Q,yand 9 are slightly in error for 7-ply and 11 -ply panels.

Parallel plies QL = O. 1 25( X: - xZ2 + ~3~ - ~ 4 ~ )

Perpendicular plies Q, = 0.1 25(x2‘ - xS2 + x42)

F3 The actual propetties of the set of plies with grain transverse tothe direction of stress are reduced by the ratio, rof the modulus of elasticity of the veneer across the grain to that along the grain; and finally, the contributions of the two sets of plies are added to give effective properties as follows:

(For stiffness calculations, r is assumed to be 0.03, and for strength calculations, r is zero, in computing the properties below).

Effective area

For stress parallel to face grain For stress perpendicular to face grain For stress at 4 5 O to face grain and for panel shear stress

A1 = A L + rAx A2 = Ax + rAL

A3 = X I

Effective moment of inertia

For stress parallel to face grain For stress perpendicular to face grain

Il = IL + rIx I2 = Ix + rIL

122



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SNZ NZSx3b03 9 3 8583Lb9 0010905 059

NZS 3603: 1 993

Effective sectional modulus

211 For stress parallel to face grain Z1 = - X1

For stress perpendicular to the face grain the outer transverse tension ply is taken as completely ineffective, but the consequent slight change of neutral axis is neglected, so that

z2 = 2(Ix + r (IL - Id) / x2 = 2(12- r i d ) / x2

where

I , =- ’ ((xi - ~ 2 ) ~ + ~ ( X I - x2)(x1 + ~ 2 ) ~ ) for all assemblies 96

Effective first moment of area

For stress parallel to face grain C?1=Q,-+rQ, For stress perpendicular to face grain 0, = Q, + rQL

F4 The full geometrical properties of cross sections apply in respect of panel shear and plywood bending at angles to the face grain (see section 6).



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SNZ NZSr3603 73 = 8583367 OOLO7Ob T95

Unsanded 3 ply

Sanded 3 ply Unsanded 5 ply

Sanded 5 ply

NZS 3603: 1993

3.4 1 .o 2.5 1.5 3.1 1.1 2.4 1.6

APPENDIX G DESIGN OF PLYWOOD PANELS SPANNING IN TWO DIRECTIONS

>

Type of Type of load support

Un iformly distributed Central point load

Simple A=Gj9d/EIw A = CgBPW3 I E Z W

M, = C49w2

Clamped A=C&@/EIW

G1 Where plywood is supported on all edges, for example on a grid system of joists and blocking, it will effectively span in two directions if the value of a parameter B is less than 1.8:

G2 For convenience the U w ratios corresponding to B = 1.8 are given in table G1.

63 Such theoretical solutions as are available for panels where B < 1.8 are given in table G2.

G4 For panels where B> 1.8, the maximum bending stress is controlled by span in the width direction and for small deflections, taking the centres of the joists as support lines, simple beam theory is adequate.

Table G1 - Maximum length to width (L/w) ratios for plate bending action in plywood

Direction of face grain Type of plywood

Along length, L Across width, w



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S N Z NZS*3603 93 m 8583169 O010907 921 m

NZS 3603: 1 993

Table G3 - Values of constants, to C7 inclusive

0.4 0.6 0.8 1 .o 1.2 1.4 1.6 2.0

c3 c4 c5

0.0003 0.001 4 0.0034 0.006 0.008 0.01 o 0.01 1 0.013

0.031 0.068 0.1 04 0.1 25 0.125 0.125 O. 125 0.125

0.0032 0.0047 0.01 2 0.016 0.01 8 0.01 9 0.020 0.020

c7

0.0001 0.0003 0.0008 0.001 5 0.0020 0.0023 O. 0025 0.0026

0.62 0.84 0.97 1 .o0 1 .o0 1 .o0 1 .o0 1 .o0



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SNZ NZSS3603 9 3 8583Lb9 OULU908 868 M

NZS 3603: 1 993

APPENDIX H LOCAL BUCKLING OF PLYWOOD ELEMENTS IN COMPRESSION

H1 ka for plywood panels

The stability factor Iqj is dependent on the slenderness ratio, Sas defined in H2.2, H2.3 and H3.2.

Table H I - Stability factor, k8 for compression

S k8

Less than 1 O 1 .o0 10 1 .o0 15 0.78 20 0.60 25 0.44

S k8

30 35 40 45 50

0.31 0.23 0.18 0.1 4 0.1 1

H2 Unloaded, edges unsupported

H2.1 Unloaded unsupported edges may occur in the gussets of a truss or frame. This type of situation should be avoided in design.

H2.2 For face grain parallel or perpendicular to the stress, the slenderness ratio is given by:

................................................................................... (Eq. HA)

where h = the unsupported length and values of A and Zare taken according to the direction of the face grain.

H2.3 For face grain at eo to the stress, the slenderness ratio is given by:

................................................................................... (Eq- H2) h S, =T

H3 Unloaded, edges supported

H3.1 A typical example of ‘unloaded, edges supported’ is the compression skin of a stressed skin panel.

H3.2 The slenderness ratio for calculation for the stability factor is given by:

................................................................................... s, = 0.126C7+5 (Eq. H3)

where C7 is given in table G3 and the stress is parallel to the length direction of the panel.

H3.3 For design purposes, C7 may be taken as 1 .O for length to width (Uw) ratios greater than half those given in table G1 which will be true for usual stressed skin panel constructions.



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SNZ NZSx3b03 93 = 8583169 OOLO909 7 T 4 = NZS 3603: 1 993

H3.4 As a design aid, the maximum width to thickness (w/t) ratios for 3-ply and 5-ply panels for which k8 = 1 .O, are given in table H2.

Table H2 - Maximum width to thickness (wb) ratios for plywood panels stable in cornpression

Direction of face grain Type of plywood

Along length, L Across width, w

3 PlY 5 PlY

15 20

20 23

127



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SNZ NZS*3603 9 3 8583369 OOLOïLO 43b

Slope of scarf Bending or tension Compression

NZS 3603: 1 993

APPENDIX J DESIGN OF END OR EDGE JOINTS IN PLYWOOD

Shear

J1 Scarf joints

Slope of scarf Bending or tension Compression

J1.l General

Shear

J1.l.l Plain glued scarf joints may be used to join plywood sheets.

1 :12 85 1 O0 1 :10 80 1 O0 1 : 8 75 1 O0 1 :5 60 1 O0

J1 .I .2 For wet or damp service conditions, plain scarf joints shall be made with glue of the appropriate class.

1 O0 1 O0 1 O0

No data

J1.2 Design strength

1:12 85 1 O0 1 :10 80 1 O0 1 : 8 75 1 O0 1 :5 60 1 O0

J1.2.1 Design strengths for scarf joints across the face grain must not be greater than the values given in table J1.

1 O0 1 O0 1 O0

No data

J1.2.2 The shear strength of table J1 apply also to scarf joints along the face grain and having a slope not greater than 1 in 8.

Table J1 - Percentages of plywood design strength transmitted across scarf joints

52 Spliced joints

52.1 General

52.1.1 Butt joints are commonly spliced with plywood plates fixed by nailing or gluing using the appropriate class of adhesive.

The joints are usually made across the grain and with the face grain of the plates parallel to that of the members being jointed.

52.1.2 When joining plywood panels, splice plates may be:

(a) Applied to one or both sides;

(b) Glued, in which case the thickness of the splice plates should be not less than the thickness of the panels being joined.



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SNZ N Z S r 3 6 0 3 93

Splice application Plywood construction

Face grain parallel to One side: direction of loading 3 plies

5 or more plies Both sides:

All constructions

8583169 OOLOî11 352

Minimum overall length of splice plate of thickness, t

30t 24t

24 t

NZS 3603: 1 993

Face grain perpendicular to direction of loading

J2.1.3 When joining timber members, splice plates should:

One or both sides: All constructions 12t

(a) Be applied to both sides; and

Bending or tension

Splice plate Splice plate on one side

Compression

on both sides

(b) Have their face grain parallel to that of the members.

Shear

52.1.4 Forthe design strengthsof table J3tO be appliciable the minimum length of splice platesfor glued joints shall not be less than those given in table J2.

50

J2.1.5 The minimum length of glued splice plates subject only to shear stresses should be 121 in all cases.

85 1 O0 1 O0

52.1.6 Splice plates of a lesser length than the minimum values given in table J2 and J2.1.5 may be used providing all strengths are reduced proportionately.

NOTE - The minimum length provisions provided by this table should not be used in conjunction with table J3 as they are not relevant to nailed splices.

52.2 Design strength

52.2.1 Design strengths for nailed or glued spliced joints made in accordance with the preceding clauses should be not greater than those given in table J3. For plywood webs, the strengths in table J3 should be taken only when the splice’plate extends the full depth between flanges.

Table J3 - Percentages of design strength transmitted across spliced butt joints

I Plywood thickness

Less than 15 mrn

Exceeding 13 mrn I

67 85 1 O0 1 O0

NOTE -This table is for use only with the appropriate section properties.

129 I

A Copyright Standards New Zealand Provided by IHS under license with SNZ Licensee=Unitec Inst of Technology/5911177001


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NZS 3603: 1 993

53 Combination of stresses Joints subject to:

(a) More than one type of stress, for example, tension and shear; or

(b) Stress reversal, for example, tension and compression should be designed for the most severe case.

J4 Secondary stresses The sum of tension and bending stresses at any joint should not exceed the design tension strength alone.

55 Other types of glued joints

55.1 Alternative types of glued joints for plywood panels are:

(a) Finger joints;

(b) Tongue and groove; and

(c) Special scarf joints.

Butt joints backed by timber framing may also be used.

55.2 Tests shall be conducted to establish characteristic strengths for the various alternative types of joints listed in J5.1.



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S N Z NZSm3b03 9 3 8583Lb9 0010913 125

NZS 3603: 1 993

THENEWZEALANDSTANDARDCERTIFICATION MARKSCHEME

The Is’ Mark appearing on a product, container or label is an assurance that the goods are manufactured under a system of supervision, control, and testing (including peribdical inspection at the manufacturer‘s works by Standards New Zealand Certification Officers) designed to ensure compliance of the commodity, process, or practice with the relevant New Zealand Standard. The New Zealand Standard Certification Mark, registered as a certification trade mark under the Trade Marks Act 1953, may be used only in terms of a licence issued by Standards New Zealand, and must be accompanied by the licence number and the NZS number.

Used correctly in conjunction with advertising the ‘SI Mark can provide a strong assurance of product quality for a manufacturer when selling his goods and thus becomes a powerful marketing tool.

Manufacturers may obtain particulars of the conditions of licensing from the Manager, Quality Sector, Standards New Zealand, Private Bag 2439, Wellington 6001.

01993 STANDARDS COUNCIL

Approved by the Standards Council on 6 September 1993 to be a New Zealand Standard pursuant to the provisions of section 10 of the Standards Act 1988.

First published: 22 September 1993

Project No. P 3603 Draft for comment No. DZ 3603 Printing code: 1000-1 993/1008/6692 Typeset by: Standards New Zealand Printed by: Wright & Carman Ltd.



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S N Z NZSx3603 9 3 I 8583169 0010914 061 H

NZS 3603:1993

I Copyright Standards New Zealand Provided by IHS under license with SNZ Licensee=Unitec Inst of Technology/5911177001


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