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S1 SLAB DESIGN (RESISTOFLEX OFFICE SHOWCASE BUILDING) (IS 456)
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Design Data
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Dimensions of the slab (c/c distance b/w supports),
fck=30
N/mm2
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Length of short span,
Lx=3.500m fy=500
N/mm2
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Length of long span,
Ly=4.500m
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Width of the supporting beam,
=350
mm
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Clear cover to main reinforcement
=25
mm
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Assume dia. of reinforcement steel
=10
mm
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Calculations
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Thickness of slab is
150
mm ;
Effective depth,
d=120
mm
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Effective span,
lx=
3.5 m (or) 3.27 m whichever is less;
d=3.270m
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ly=
4.5 m (or) 4.27 m whichever is less;
d=4.270m
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(ly / lx)=1.31<2 ;
Here, (ly / lx) is less than 2, Hence design the slab as two way slab
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Load Calculations
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Dead Load of slab
=
0.15 x 25
=3.75
KN/m2
Dust Load on slab
=0
KN/m2
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Finishes load on slab
=1.20
KN/m2
Other load on slab
=0
KN/m2
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Live Load on slab
=7.5
KN/m2
(Worst Load Case)
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Total Dead load acting on the Structure
=4.95
KN/m2
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Total live load acting on the Structure
=7.5
KN/m2
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Factored Design Load
w=18.68
KN/m2
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Support Condition
(Type of panel according to support condition)
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One Long Edge Discontinuous
For this support condition,
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Short span coefficient for (ly / lx) =
1.31,
Long span coefficient,
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For negative moment,
ax=0.0576
For negative moment,
ay=0.037
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For positive moment,
ax=0.0443
For positive moment,
ay=0.028
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Moment Calculation
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Max. BM per unit width,
Mx=
ax w lx2
&My=
ay w lx2
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MuMu / bd2pt
Ast, req
Ast , min=
(0.12/100) bD
=180
mm2
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KNmN/mm2%mm2
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For Short Span,
Reinforcement details
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At mid span,
8.850.610.173208
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At supports,
11.510.800.229275
Provide
Y8@150
mm c/c
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For Long span,
for short span
(Ast pro. =
335
mm2 )
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At mid span,
5.590.460.130156
Provide
Y8@150
mm c/c
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At supports,
7.390.610.173208
for long span
(Ast pro. =
335
mm2 )
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Check for Deflection
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Percentage of tension reinforcement
=0.28%
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fs=
0.58 fy (Ast req / Ast pro)
=179.9952409
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Refer Fig. 4 of IS 456,
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Modification factor
=1.6
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Allowable (Span / deff ) ratio
=41.6
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Effective depth required
=79
mm
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<
d prov.
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Hence OK
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