NZBridges 2012 Hicks Presentation

NZBridges 2012, Wellington, 29 - 30 October 2012 1

Proposed Joint Bridge Design Standard AS/NZS 5100.6

for Steel and Composite Construction

Dr Stephen Hicks New Zealand Heavy Engineering Research Association (HERA),

General Manager Structural Systems


AS5100 revision

• Standards Australia project with a duration of 3-years

• Project kick-off November 2010

• Initial scope of project:

• General reviewing and updating all Parts.

• Updating Part 2 to be aligned to the earthquake code

• Updating Part 4 to address new bearing and expansion joint materials.

• Updating Part 5 in line with changes to AS 3600.

• Following acceptance of proposals submitted to Standards Australia

in February 2012, two new parts are being developed in parallel with

the revision of existing AS5100

• Due to its size, AS5100 to be published in a lever arch file format for

ease of future maintenance.

• From NZ stakeholder consultation, including the Steel Bridge

Development Group, confirmation from Standards New Zealand to

revise Part 6 as a joint AS/NZS Standard


Proposed suite of AS5100 parts

Standard Committee

responsible

Description

AS 5100.1 to .9 BD-090 Bridge Design

AS 5100.1 BD-090-01 Scope and General Principles

AS 5100.2 BD-090-02 Design Loads

AS 5100.3 BD-090-03 Foundations (DPC ended 5 March 2012)

AS 5100.4 BD-090-04 Bearings and Deck Joints

AS 5100.5 BD-090-05 Concrete

AS/NZS 5100.6 BD-090-06 Steel and Composite Construction

AS 5100.7 BD-090-07 Rating

AS 5100.8 BD-090-08 Rehabilitation

AS 5100.9 BD-090-09 Timber Bridges


AS/NZS 5100.6

• Kick-off meeting March 2011

• Draft for Public Comment document expected early 2013

• Committee Constitution:

Stephen Hicks HERA (Chair) Peter Selby-Smith Cement Concrete &

Aggregates

Australia

Anthony Ng BOSMA Arun Syam OneSteel

Kumar

Ponnampalan

AUSTROADS Frank Rapattoni BOSMA

Brian Uy UWS Peter Key ASI

John Hilton Aurecongroup Gary Preddey Atlantic Civil

Ken Wheeler Association of

Consulting

Engineers Australia

Adrian La Manna Standards Australia


Scope and Application

• Sets out minimum requirements for design of the structural

steelwork in bridges (wrought and cast iron structures may be

checked in accordance with this Standard using appropriate

capacity reduction factors)

• Standard applies to the design of other steel components of

bridges including steel piers, steel railings and sign

structures.

• Does not cover the following structures, members and

materials:

• Bridges with orthotropic plate decks.

• Cold-formed members other than those complying with AS 1163.

• Steel members for which the value of yield stress fy used in design exceeds 690 MPa

(previously 450 MPa).

• Steel elements, other than packers, less than 3 mm thick.


Acceptance of steels

• Test reports or test certificates that comply with the minimum

requirements of the appropriate AS and AS/NZS Standards

shall constitute sufficient evidence of compliance with these

Standards

• Test reports or test certificates may be provided by the

manufacturer or an independent laboratory accredited by

signatories to the International Laboratory Accreditation

Corporation (Mutual Recognition Arrangement) (ILAC (MRA))

or the Asia Pacific Laboratory Accreditation Cooperation

(APLAC) on behalf of the manufacturer.

• In the event of a dispute as to the compliance of the steel with

any of the AS and AS/NZS Standards, the reference testing

shall be carried out by independent laboratories accredited by

signatories to ILAC (MRA) or APLAC


Steel types that comply with AS/NZS 5100.6

• Australia/New Zealand

• AS/NZS 1163 Hollow sections 250 MPa < fy ≤ 450 MPa

• AS/NZS 1594 Plate, strip, sheet floorplate 170 MPa < fy ≤ 380 MPa

• AS/NZS 3678 Plate and floorplate 200 MPa < fy ≤ 450 MPa

Includes weathering steel AS/NZS 3678-WR350 fy = 340 MPa for t ≤ 50mm

• AS/NZS 3679.1 Flats and sections 280 MPa < fy ≤ 360 MPa

• AS/NZS 3679.2 Welded sections 280 MPa < fy ≤ 340 MPa

• AS 3597 Plate 500 MPa < fy ≤ 690 MPa

• NZS 3404.1 currently permits the following

overseas steels

• EN 10025-2, EN 10025-2 and EN 10025-4 275 MPa < fy ≤ 560 MPa

• JIS G 3106 and JIS G 3136 215 MPa < fy ≤ 460 MPa


Ultimate Limit State conditions cover: • Provision of strength (STR) • Loss of Static equilibrium (EQU) • Failure from excessive deformation of

ground (GEO) • Fatigue failure (FAT) Selection of Ultimate Limit State loads: • Design life = reference period R

(normally taken as 50 years for buildings)

• Return period T - R / ln(1-p) R / p where p = probability of exceedance during the reference period.

• Load factor ≥ 1.0

Design for the Ultimate Limit State

pf 10-6 10-5 10-4 10-3 10-2 10-1

4.75 4.27 3.72 3.09 2.32 1.28

pf = 7.2×10-5 ≡ =3.8 (typically used for

ULS considerations).

ULS SLS

pf ≈ 10-β


Basis of Load and Strength capacity reduction

factors

• Normal distribution usually taken • Characteristic value

• Mean value if variability small • Upper value (normally 95% fractile) if variability

is not small • Design value based on probability of failure

• Log-normal distribution usually taken (resistance doesn’t have negative values)

• Characteristic (or nominal) value for resistance based on lower value (5% fractile)

• Design value based on probability of failure. For large sample of data and a normal distribution

• 5% fractile = 1.64 σR • Design value = 0.8 x 3.8 σR = 3.04 σR ( 0.1%

probability of observing lower value)

Loads Material and product properties

S Sk Sd

-S β σS

R Rd Rk

-R β σR

S and R from ISO2394

=1/R S

Rk / Rd =R = 1/


Structural reliability analyses of beams in bending by UWS

and HERA

• Analyses on beam tests that

have compact, not-compact

and non-compact cross-

sections show: • capacity factor of 0.90 given in AS 4100

and AS 5100.6 for beams in bending

are on the conservative side for EN

10034 JIS G 3192 and JIS A 5526

manufacturing Standards.

• Design practice that has been adopted

in NZS 3404.1 for the last 35-years is

supported (where no differentiation is

made with respect to the capacity

factors when steel complying with EN

10025, JIS G 3106 and JIS G 3136 is

used).

• Proposed to introduce

overseas steels appendix in

AS/NZS 5100.6 with

minimum product conformity

requirements equivalent to

AS/NZS steels

Parameter EN10034: 1993

JIS G

3192:

2005

JIS A

5526:

2005

AS 5100.6

AS/NZS

1365:1996

Depth (h)

(mm) -2 -2 -h/50

Width (b)

(mm)

b≤110

110<b≤21

0

-1

-2 -2.5 -b/100

Web

thickness

(tw) (mm)

tw<7

7≤tw<10

-0.7

-1 -0.7

4.5<t≤6

6<t≤10

-0.85

-0.9 Flange

thickness (tf)

(mm)

-1 -1

2.6 2.8 3 3.2 3.4 3.6 3.8 4 4.20.4

0.5

0.6

0.7

0.8

0.9

1

1.1

Reliability index ()

Cap

acit

y f

acto

r

Steel ()

Compact sections manufactured to EN 10034

manufacturing tolerances ϕ=0.94 at β = 3.04


Concrete types covered by AS/NZS 5100.6

• Aligns with AS 5100.5 and is applicable to

the following characteristic compressive

strengths of standard strength grades:

20 MPa, 25 MPa, 32 MPa, 40 MPa, 50 MPa,

65 MPa, 80 MPa and 100 MPa


Corrosion Resistance & Protection


Effective breadth

1 3 2 4

L1 L2 L3

L1/4 L1/4 L2/4 L2/2 L2/4

be

ff,0

be

ff,2

be

ff,1

L1/2

be

ff,0

be

ff,1

be1 be2

b1 b2

b0

b0

beff

Key

1 Le = 0.85 L1 for beff,1

2 Le = 0.25 (L1 + L2) for beff,2

3 Le = 0.70 L2 for beff,1

4 Le = 2 L3 for beff,2


Rigorous Structural Analysis

No

Material

behaviour

Geometric

behaviour

Imperfections

Example of use

1 linear linear no elastic shear lag effect, elastic

resistance

2 non linear linear no plastic resistance in ULS

3 linear non linear no critical plate buckling load

4 linear non linear yes elastic plate buckling resistance

5 non linear non linear yes elastic-plastic resistance in

ULS

Type of

imperfection Component

global member

with length ℓ

global

longitudinal

stiffener with

length a

local panel or

subpanel

local stiffener

or flange

subject to twist

Model

with yielding

plateau

with strain-

hardening


Corrugated Web Girders


Use of steel with fy ≥ 420 MPa

A

B

C

(C) PNA in

web

MRd = Mpl,Rd


Resistance of headed stud connectors

• Structural reliability analyses

conducted by HERA which

considered international push test

data (n = 108) and extended

equations to 16 MPa < f’cy ≤ 100 MPa

(previously ≤ 40 MPa).

• No other international Standard

provides design equations to this

upper end of f’cy

or

• whichever is smaller, where • dbs is nominal shank diameter of a shear stud,

but 15.9 ≤ dbs ≤ 25 mm, fuc is UTS of shear

connector, but not greater than 500 MPa, f’cy is

the characteristic strength of the concrete, but

not greater than 100 MPa and Ec is modulus

of elasticity for concrete, and may be taken to

be for 5050√f’cy for f’cy ≤ 40

150

250

250

150 150260

Cover 15

P

ucfdf 2

bsks62.0

ccy

2

bsksE fd.f 310


Combined shear and tension

• Where headed stud connectors are subject

to both tension and shear the following

rules apply:

• if N*u ≤ 0.1fks, the tensile force may be neglected;

• if N*u > 0.1fks the following interaction between the design

shear and design tension shall be satisfied.

0.185.0

35

*35

*

ks

L

ks

u

f

V

f

N


Horizontally lying studs examples


Failure modes due to stud position


Detailing & Design Equations for horizontally lying

studs


Transverse reinforcement – Option of using strut &

tie modelling


Potential shear planes


Composite columns

• More generous width-to-thickness ratio’s

permitted for composite column design cf.

other international Standards

• Higher concrete strengths permitted: 100

MPa cf. 50 MPa in EN 1994-2 (Eurocode 4)

• Bond strengths given for longitudinal shear

connection

Type of cross section bond (MPa)

Completely concrete encased steel sections 0.30

Concrete filled circular hollow sections 0.55

Concrete filled rectangular hollow sections 0.40

Flanges of partially encased sections 0.20

Webs of partially encased sections -


cross-section b

0

0.5

-0.5

0

0

0

%3s

%6%3 s

20 100

1,0

0,8

0,6

0,4

0,2

60 140

-0.5

0

0.5

ccryrysus fAfAfAN

180

buckling about

strong axis

buckling about

weak axis

85,0

00,1

85,0

85,0

00,1

00,1

Composite columns verification for axial

compression

For kf = 1.0 b


N

M

2

*N

*N

Rd,plM Rdmax,M

usN

A

B

D

As a simplification, the interaction

curve may be replaced by a

polygonal diagram given by the

points A to D.

C

Determination of interaction curve


Filler plates

• Where bolts or rivets transmitting load in

shear and bearing pass through packing of

total thickness tp greater than one-third of

the nominal diameter d, the design shear

resistance should be multiplying by a

reduction factor p given by:

0.1but 33

9

p

p

ptd

d


S-N curves simplified

S-N Curve for Normal Stress S-N Curve for Shear Stress


Functional and Essential Tolerances


Conclusions

• Bridge design – Part 6: Steel and composite

construction, only part of AS 5100 suite being

revised as a joint AS/NZS Standard

• Proposed that overseas steels currently recognized

in NZS 3404.1, together with weldability and brittle

fracture provisions, to be covered in an appendix.

• Following the international trend of using less

natural resources, rules for higher strength steel

and concrete given.

• New design rules provide greater alignment with

international best practice and, in some cases,

improvements are given.


Where can I get further information?

http://www.standards.org.au



http://www.standards.co.nz/



[email protected]

http://www.hera.org.nz/

Documents

NZBridges 2012 Hicks Presentation