Design of Slabs

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Design of Slabs
- Types of Slabs - One-way Slabs - Two-way Slabs
SLAB_01
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Types of Slab
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One-way Slab
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Design of One-way Slab (L gt 2S)
Minimum Thickness (ACI)
SLAB_04
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ACI Design Provision
SLAB_05
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If A and B are fiexed against rotation,
SLAB_06
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Example Design one-way slab as shown below to
carry the live load 500-kg/m2
fc 210 kg/cm2, fy 2,400 kg/cm2
0.4 2400/7000 0.74 min h 400(0.74)/24
12.3 cm USE h 13 cm DL 0.13?2400 312kg/m2
wu 1.4(312) 1.7(500) 1,286.8
kg/m2 clear span 4 - 0.3 3.7 m Mu
(1,286.8)(3.7)2/10 1,762 kg-m rmax
0.75rb 0.75(0.0454) 0.0341
SLAB_07
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USE RB9 with 2 cm covering d 13-2-0.45 10.55
cm
As rbd 0.0077(100)(10.55) 8.16 cm2/m Select
RB9_at_0.07 (As 9.28 cm2/m) Temp. steel
0.0025(100)(13) 3.25 lt 9.28 cm2/m
OK Select RB9_at_0.18 (As 3.53 cm2/m)
SLAB_08
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SLAB_09
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Design of Two-way Slab (L lt 2S)
Reinforcement Steel As ? f 6 mm ? Temp.
steel Max. Spacing ? 3 t ? 45 cm Min. Spacing
? f main steel ? 4/3 max agg. ? 2.5 cm
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Load transfer from two-way Slab
SLAB_11
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Moment Coefficient Method
Middle strip moment MM CwS2 Column strip
moment MC 2MM/3
SLAB_12
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??????????????????????????? ( C )
????????
???????
??????????? m
??????????
1.0
0.9
0.8
0.7
0.6
0.5
????????? ?????????-?????????????
-???????????????? ?????????????????????
0.033 - 0.025
0.040 - 0.030
0.048 - 0.036
0.055 - 0.041
0.063 - 0.047
0.083 - 0.062
0.033 - 0.025
????????????????????????? ?????????-?????????????
-???????????????? ??????????????????
???
0.041 0.021 0.031
0.048 0.024 0.036
0.055 0.027 0.041
0.062 0.031 0.047
0.069 0.035 0.052
0.085 0.042 0.064
0.041 0.021 0.031
??????????????????????? ?????????-?????????????
-???????????????? ????????????????????
?
0.049 0.025 0.037
0.057 0.028 0.043
0.064 0.032 0.048
0.071 0.036 0.054
0.078 0.039 0.059
0.090 0.045 0.068
0.049 0.025 0.037
SLAB_13
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??????????????????????????? ( C )
????????
???????
??????????? m
??????????
1.0
0.9
0.8
0.7
0.6
0.5
??????????????????????? ?????????-?????????????
-???????????????? ????????????????????
?
0.058 0.029 0.044
0.066 0.033 0.050
0.074 0.037 0.056
0.082 0.041 0.062
0.090 0.045 0.068
0.098 0.049 0.074
0.058 0.029 0.044
??????????????????????? ?????????-?????????????
-???????????????? ????????????????????
?
- 0.033 0.050
- 0.038 0.057
- 0.043 0.064
- 0.047 0.072
- 0.053 0.080
- 0.055 0.083
- 0.033 0.050
SLAB_14
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Bar detailing in slab
L1/3
L2/3
?????????????????
L1/7
L1/4
L2/4
L1
L2
Bar detailing in beam
L1/3
L2/3
L1/8
L1/8
L1
L2
SLAB_15
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????????????????????????
SLAB_16
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Example Design two-way slab as shown below to
carry the live load 300-kg/m2
fc 240 kg/cm2, fy 2,400 kg/cm2
Min h 2(400500)/180 10 cm
DL 0.10(2,400) 240 kg/m2
wu 1.4(240)1.7(300) 846 kg/m2
m 4.00/5.00 0.8
As,min 0.0018(100)(10) 1.8 cm2/m
SLAB_17
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Max. M C w S 2 0.064 ? 846 ? 4.02 866
kg-m/1 m width
d 10 - 2(covering) - 0.5(half of DB10) 7.5 cm
As 0.0045(100)(7.5) 3.36 ??.2 gt As,min
???????????????????? DB10_at_0.20 (As3.90 ??.2)
SLAB_18
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Long span
-M(????????????)
-M(?????????)
M
Moment coeff. C
0.025
0.037
0.049
Max. M C w S 2 0.049 ? 846 ? 4.02 663
kg-m/1 m width
d 10 - 2(covering) - 1.5(half of DB10) 6.5 cm
As 0.0046(100)(6.5) 2.97 ??.2 gt As,min
???????????????????? DB10_at_0.20 (As3.90 ??.2)
SLAB_19
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?????????????????????????????????
?????????????? Vu wuS/4 (846)(4.0)/4
846 ??./?.
SLAB_20
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SLAB_21