One Way Slab Design

LARSEN & TOUBRO LIMITED ECC Division - GES

PART -4

DATE1861B-CS-05-00304

TITLE: HOSPITAL BUILDING - DESIGN OF PLAZA BEAMS & SLABSDESIGNED

SIDRA MEDICAL AND RESEARCH CENTER,QATAR DOCUMENT NO

ASN/STN CSR/MDS

PROJECT:21/05/09

CHECKED SHEET

(AT PLAZA LEVEL IN TOWER BLOCK OF HOSPITAL BUILDING)

ONE WAY SLAB DESIGN

7

LARSEN & TOUBRO LIMITEDECC Division - GES

DOCUMENT NO DATE

1861B-CS-05-00304CHECKED SHEET

2.0 DESIGN OF ONE WAY SLABS

In this section the design of slab for beam slab portion of part -4 is presented. This portion consist of oneway slabs supported by main beams and secondary beams. Slab thickness considered are 200 and 300mm. Analysis and design carried out as per BS 8110.

Unit weight of the concrete = kN/m3

Loads ConsideredSuperimposed Dead load = kN/m2

Live load = kN/m2

Soil unit weight (wet) = kN/m3

21/0509

5.55

20

25

PROJECT:

TITLE:

SIDRA MEDICAL & RESEARCH CENTER, DOHA

DESIGNED

STNHOSPITAL BUILDING - DESIGN OF PLAZA BEAMS & SLABS

CSR/MDS

8

9


DOCUMENT NO DATE


Design of slab panels S5,S6,S7,S8 and S9

The design moments & shear forces are arrived based on clause 3.5.2.4 of BS 8110 Part 1 provisions by considering 1m wide strip of the one way slab.Loads are as follows.

Slab thickness = 200 mmSelf weight = 5 kN/m2

Super imposed dead load = 5.5 kN/m2

(a) Total Dead load (DL) = 10.5 kN/m2

(b) Live load (LL) = 5 kN/m2

Design factored load (Fu) =1.4DL+1.6LL = 22.7 kN/m2

Load for serviceability condition, (Fs) =DL+LL = 15.5 kN/m2

21/0509

CSR/MDS

PROJECT: SIDRA MEDICAL & RESEARCH CENTER, DOHA


STN

Moment and Shear coefificients (Table 3.12, pg 37)

0 S5 S6 S7 -0.063 S8 S9

0.063

L5= L6= L7= L8= L9=

(a) Moment coefficients

S5 S6 S7 0.5 S8 S9

L5= L6= L7= L8= L9=

(b) Shear coefficients

-0.063

6m 6m 5.2m 5.2m

-0.063

0.063

0.5

5.2m6m

-0.086

5.2m6m

-0.063

0.5

0.086 0.063 0.063

5.1m

0.60.4 0.5

5.1m

10


DOCUMENT NO DATE


21/0509

CSR/MDS



STN

Bending moment and shear force diagram

(a) Strength case

Bending moment = (FuxL) x L x moment coefficient

-51.5

51 51.5(a) Bending Moment(kN-m)

Shear Force = (FuxL) x shear coefficient

46 82 68 68 59

-38.7

38.7

-38.7

38.7

-70.3

50.8

-51.5

69 68 68(b) Shear Force(kN)

(b) Seviceability case

Bending moment = (FsxL) x L x moment coefficient

-35.2

35 35.2(a) Bending Moment(kN-m)

Design for Flexure

Slab section is designed for maximum moment from the above calculation.Grade of Concrete, fcu = 40 N/mm2

Yield Strength of Steel, fy = 420 N/mm2

Cover to reinforcement = 30 mmSlab thickness, D = 200 mm

(a) Top Reinforcement (main bars)Maximum Hogging moment = 70.3 kN-mEffective depth, d = 162 mmBreadth, b = 1000 mm

-26.4

26.4 26.4

59 59

-48 -35.2 -26.4

34.7

11


DOCUMENT NO DATE


21/0509

CSR/MDS



STN

K = (Mu / fcub * d2 ) = 0.07 <�K'�(0.156)Z = Min[0.95d, d{0.5 + sqrt(0.25-K/0.9)}] = 148.9 mm

Area of Steel required, (Mu/(0.87fy*z) = 1292 mm2

Req�%Pt = 0.80 %Min. Ast required (0.13%) = 211 mm2

Ast provided = 1340 mm2

Provide mm dia bar at mm C/C as Top reinforcement (main bars)

(b) Bottom Reinforcement (main bars)Maximum Sagging moment = 51.5 kN-mEffective depth, d = 162 mm

Breadth, b = 1000 mmK = (Mu / fcub * d2 ) = 0.05 <�K'�(0.156)

Z = Min[0.95d, d{0.5 + sqrt(0.25-K/0.9)}] = 152.6 mmArea of Steel required, (Mu/(0.87fy*z) = 923 mm2

Req�%Pt = 0.57 %2

15016

Min. Ast required (0.13%) = 211 mm2


Provide mm dia bar at mm C/C as Bottom reinforcement (main bars)(c) Secondary reinforcement

Minimum reinforcement shall be provided both top and bottom secondary reinforcemetMin Percentage of Ast = 0.13 % Ast min = 211 mm2


Provide mm dia bar at mm C/C on as secondary bars both at top and bottom

Check for Shear

Allowable�shear�stress�in�concrete (using Table 3.8, pg 30 BS8110 part1)

vc = 0.79[100As/(bvd)]1/3 (400/d)1/4/�m

(multiplication factor for concrete grade > 25 = (fcu/25)1/3 ) vc = N/mm2

(where, As = , bv = 1000 d = , �m = 1.25)Maximum shear, v = Vu/bd

(Vu = 82 kN, b=1000, d= ) v = N/mm2

< ��vc Hence Safe

Check for deflection (Cl 3.4.6.3 of BS8110 part 1)

Basic span/effective depth ratio from table 3.9 = 20(conservatively taken for simply supported condition)

Modification factors(a) For Tension reinforcement (Using Table 3.10 of the code)

10 150

0.87

16 150

1340

162 0.50

162

12


DOCUMENT NO DATE


21/0509

CSR/MDS



STN

Design service stress, fs = 2fyAs req/(3As prov �b)

= 161 N/mm2

where, As req = mm2

As prov = mm2

�b = for 20%redistribution

Mu/bd2 = 1.96

Modification factor = 0.55 + (477-fs) / [120(0.9+Mu/bd2] < 2.0= 1.47 < 2.0

(b) For Compression reinforcement (Using Table 3.11 of the code)

As`prov = mm2 100As`prov/bd = Modification factor = 1 + (100As`prov/bd) / (3+ 100As`prov/bd) < 1.5

= < 1.5Allowable span/effective depth ratio = 20 x 1.47 x 1.22

1340 0.83

1.22

13401.2

923

= 35.8Actual ratio = 5.1 x 1000 / 162 = 31.5 Hence safe against deflection

Check for crack width

Crack width is calculated and and attached seperately

Note: Same design shall be followed for similar one way panals such as S18, S19, S20, S21, S22, S23S13,S14,S15,S16,S17,S1,S2

13


DOCUMENT NO DATE1861B-CS-05-00304 21.05.09

CHECKED SHEET

Design of slab panels S4 (Refer section 9a-9a)

The design moments & shear force are arrived by taking the slab as a simply supported slab considering 1m wide strip of the one way slab.Design loads are as follows.

Slab thickness = 300 mmSelf weight = 7.5 kN/m2

Super imposed dead load = 0 kN/m2

1 m Soil filling (20x1) = 20 kN/m2

(a) Total Dead load (DL) = 27.5 kN/m2



Load for serviceability condition, (Fs) =DL+LL = 32.5 kN/m2

Clear span, L = 4.3 mEff ti S 4 6

DESIGNED

STN


TITLE: HOSPITAL BUILDING - DESIGN OF PLAZA BEAMS & SLABSCSR/MDS

Effective Span = 4.6 mMaximum Span moment, Mu = FuL

2/8 = 107 kN-mMaximum Shear force, Vu = FuL/2 = 100 kN

Moment under serviceability condition, Mu = FsL2/8 = 75 kN-m

Design for Flexure

Slab section is designed for maximum moment.Grade of Concrete, fcu = 40 N/mm2



(a) Bottom Reinforcement (main bars)Maximum Sagging moment = 107 kN-mEffective depth, d = 262 mm


Z = Min[0.95d, d{0.5 + sqrt(0.25-K/0.9)}] = 249 mmArea of Steel required, (Mu/(0.87fy*z) = 1182 mm2



Provide mm dia bar at mm C/C as Bottom reinforcement (main bars)(b) Top reinforcement

Provide 50% of bottom steel = 670 mm2

16 150

14



CHECKED SHEETDESIGNED

STN



Min Percentage of Ast = 0.13 % Ast min = 341 mm2


Provide mm dia bar at mm C/C on as top reinforcement (main bars)(c) Secondary reinforcement

Minimum reinforcement shall be provided both top and bottom secondary reinforcemetMin Percentage of Ast = 0.13 % Ast min = 341 mm2



Check for Shear


vc = 0.79[100As/(bvd)]1/3 (400/d)1/4/�m

(multiplication factor for concrete grade > 25 = (fcu/25)1/3 ) vc = N/mm2

16 150

0.66

10 150


(Vu = kN, b=1000, d= ) v = N/mm2



Basic span/effective depth ratio from table 3.9 = 20(for simply supported condition)



= 247 N/mm2

where, As req = mm2

As prov = mm2

�b =Mu/bd2 = 1.57


(b) For Compression reinforcement (Using Table 3.11 of the code)As`prov = mm2 100As`prov/bd =

Modification factor = 1 + (100As`prov/bd) / (3+ 100As`prov/bd) < 1.5


= 30.4

100

1340 262

262 0.38

11821340

1

1340 0.51

1.15

15



CHECKED SHEETDESIGNED

STN



Actual ratio = 4.6 x 1000 / 262 = 17.6 Hence safe against deflection


Crack width is calculated and and attached seperately.

Note: Same design shall be followed for similar one way panals such as S11

16


DOCUMENT NO DATE

1861B-CS-05-00304 21.05.09CHECKED SHEET

Design of slab panels S3 (Refer section 20a-20a)

The design moments & shear force are arrived by taking the slab as a simply supported slab considering 1m wide strip of the one way slab.Design loads are as follows.

Slab thickness = 300 mmSelf weight = 7.5 kN/m2

Super imposed dead load = 5.5 kN/m2

(a) Total Dead load (DL) = 13 kN/m2



Load for serviceability condition, (Fs) =DL+LL = 18 kN/m2

Clear span, L = 5.5 mEff ti S 5 8



CSR/MDSSTN

Effective Span = 5.8 mMaximum Span moment, Mu = FuL

2/8 = 99 kN-mMaximum Shear force, Vu = FuL/2 = 72 kN

Moment under serviceability condition, Mu = FsL2/8 = 68 kN-m

Design for Flexure

Slab section is designed for maximum moment.Grade of Concrete, fcu = 40 N/mm2



(a) Bottom Reinforcement (main bars)Maximum Sagging moment = 99 kN-mEffective depth, d = 262 mm


Z = Min[0.95d, d{0.5 + sqrt(0.25-K/0.9)}] = 249 mmArea of Steel required, (Mu/(0.87fy*z) = 1089 mm2



Provide mm dia bar at mm C/C as Bottom reinforcement (main bars)(b) Top reinforcement

Provide 50% of bottom steel = 670 mm2

16 150

17


DOCUMENT NO DATE




CSR/MDSSTN

Min Percentage of Ast = 0.13 % Ast min = 341 mm2


Provide mm dia bar at mm C/C on as top reinforcement (main bars)(c) Secondary reinforcement

Considering the irregular shape and support conditions for this slab, provide higher reinforcementMin Percentage of Ast = 0.13 % Ast min = 341 mm2



Check for Shear


vc = 0.79[100As/(bvd)]1/3 (400/d)1/4/�m

(multiplication factor for concrete grade > 25 = (fcu/25)1/3 ) vc = N/mm20.66

16 150

16 150


(Vu = 72 kN, b=1000, d= ) v = N/mm2



Basic span/effective depth ratio from table 3.9 = 20(for simply supported condition)



= 228 N/mm2

where, As req = mm2

As prov = mm2

�b =Mu/bd2 = 1.44


(b) For Compression reinforcement (Using Table 3.11 of the code)As`prov = mm2 100As`prov/bd =

Modification factor = 1 + (100As`prov/bd) / (3+ 100As`prov/bd) < 1.5


= 32.9

13401

1340 0.51

1.15

1340 262

262 0.28

1089

18


DOCUMENT NO DATE




CSR/MDSSTN

Actual ratio = 5.8 x 1000 / 262 = 22.1 Hence safe against deflection


Crack width is calculated and and attached seperately.

19


Calculation for crack width (For slab panal - S5)

Moment due to service load = kNmWidth of slab (b) =Overall depth of slab (h) =Area of steel provided (As) = mm2

Clear cover to tension steel provided (c) =Diameter of bar provided on the tension face (�) =Effective depth of slab (d) = 200-30-16/2 =Spacing of steel (s) = mm c/cAs per BS8110-2:1985 Design Surface Crack Width

Wcr = 3acr�m/(1+2(acr-Cmin)/(h-x))Where

x = depth of neutral axis = mm61 6

150

30 mm16 mm162 mm

48.01000 mm200 mm1340

TITLE: Hospital Building - Crack width calculation DESIGNED CHECKED SHEET

STN CSR/MDS

PROJECT: SIDRA MEDICAL AND RESEARCH CENTER,QATAR DOCUMENT NO DATE1861B-CS-05-00304 21/0509

x = depth of neutral axis. = mmfs = the tensile stress in the reinforcement.

= M(d-x)/I = N/mm2

�1 = Strain at the level considered, calculated ignoringthe stiffening of the concrete in the tension zone.�1 = (h-x)fs/Es(d-x) =

�m = average steel strain at the level considered,�1 - b(h-x)(a-x)/(3EsAs(d-x)) =

a = distance from the compression face to the point atwhich crack width is being calculated, and =

Actual crack width:

acr = distance from the point considered to the surfaceof the nearest longitudinal bar = mm

Wcr = Crack width = mm

Allowable crack width = mm

HENCE SAFE

76.1

0.206

0.300

61.6

253

0.00174

0.00151

200 mm

20







150

30 mm16 mm262 mm

75.11000 mm300 mm1340


STN CSR/MDS

PROJECT: SIDRA MEDICAL AND RESEARCH CENTER,QATAR DOCUMENT NO DATE1861B-CS-05-00304 21/5/09


= M(d-x)/I = N/mm2




Actual crack width:




HENCE SAFE

76.1

0.179

0.300

82.4

239

0.00145

0.00112

300 mm

21







150

30 mm16 mm262 mm

68.11000 mm300 mm1340


STN CSR/MDS

PROJECT: SIDRA MEDICAL & RESEARCH CENTER, DOHA DOCUMENT NO DATE1861B-CS-05-00304 21/5/09


= M(d-x)/I = N/mm2




Actual crack width:




HENCE SAFE

76.1

0.158

0.300

82.4

216

0.00131

0.00098

300 mm

22

Documents

One Way Slab Design