Slab Design
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Transcript of Slab Design
CARMEL B. SABADO CE-162 PROF. GERONIDES P. ANCOGBSCE-5 2nd Excel Program SEPT. 6, 2009*note:the boxes in yellow should be inputed by the designer,while blue ones are computed by the program. =)
****====DESIGN OF ONE-WAY SLAB====****
4.6 m 4.6 m
GIVEN:
27.5 Mpa
414 Mpa
23.5 1) L / 20 ; simply supported
Slab live load = 4.8 kPa 2) L / 24 ; one end continuous
clear span,L = 4.6 m 3) L / 28 ; two end continuous
main bar diameter = 10 mm Ø 4) L / 10 ; cantilever
temp. bar diameter = 8 mm Ø
TYPE OF SLAB SECTION: 3 h = L / 28 ; TWO END CONTINUOUS
h = L
= 164.2857 mm28
say h = 165 mm
COMPUTE LOADS:DEAD LOAD(DL)
= 3.8775 Kpa
assume floor finish = 25 mm
= 0.5875 Kpa
total DL = 4.465 KPa
LIVE LOAD(LL)
service load = 4.8 Kpa
wu = 1.2DL + 1.6LL = 13.038 Kpa
COMPUTE MOMENTS:
coefficients, c L(m) w(kPa) (kN.m/m)0.111111111 4.6 13.038 30.653786670.071428571 4.6 13.038 19.706005710.041666667 4.6 13.038 11.49517
COMPUTE FOR ρ:
Concrete,fc' =
Steel,fy =
Unit weight of concrete,wc = kN/m3
self weight = wch
assume floor finish = ywc
M = cwL2
= 0.0033816
= 0.0031667
= 0.00316669
0.02129829
main bar reinforcement = 78.5398163
temp bar reinforcement = 50.2654825
COMPUTE THE REQUIRED As AND SPACING OF BAR REINFORCEMENTSinterior support at mid-span exterior support
= 30.653787 19.706006 11.49517 (kN-m/m)
d = h - (20+Ø/2) = = 120 120 120
= 2.3652613 1.5205251 0.886972994 ρ = = 0.0060358 0.0038007 0.002184714 use ρ = 0.0060358 0.0038007 0.003166693
= 724.29727 456.08248 380.0032059 s = 1000Ao/As = 108.43589 172.20529 206.6819835
TEMPERATURE BAR SPACING REQUIREMENT:
fy < 414MPa = 0.002
fy = 414MPa = 0.0018
fy > 414MPa = 0.0018(414)/fy
MINIMUM RHO FOR TEMPERATURE BARS:
= 200/fy
= 0.48309179
= 0.0018
= 216
temp bar spacing = 215
SLAB DETAILS FOR BENDING OF REINFORCEMENTSfixed bar spacing at mid-span, s = 150
= 456.0824839
523.5987756design is ok!!!=)
at exterior support
= 349.0658504
= 380.0032059design is not safe!!!=(
provide extra bars,n = 1
= 427.6056667design is ok!!!=)
at interior support
= 698.1317008
= 724.2972694design is not safe!!!=(
provide extra bars, n = 2
= 855.2113335design is ok!!!=)
1.4/ fy
√¯fc'/ 4fy
use ρmin
Mu =
(mm2)
Ru = Mu/(.9bd2)
As = ρbd (mm2)
ρtemp.
ρtemp.
ρtemp.
ρmin
ρtemp.
As,temp =ρtempbd (mm2)
(mm2)
As(required)
As(actual) = 1000Ao/s(fixed)
Ap = As(actual)2/3
As(required)
Ap = Ap + n(Ao)
Ap = As(actual)4/3
As(required)
Ap = Ap + n(Ao)
ρmax=. 75[ .85 fc ' β1600fy(600+ fy ) ]=
Slab Details Scheme 1: Bending of reinforcements
10 mm Ø bent 2/3 spaced @150 mm
1 -extra top bar is needed 2 -extra top bars are needed
165mm
1 8 10 mm Ø bent 2/3 spaced @-extra top bar is needed mmØ temp bars @ 150 mm
215 mm
2-extra top bars are needed
Slab Details Scheme 2: Cutting of reinforcements
10 mmØ 10 mmØ 10 8 mmØ 190 oc 380 oc 190 oc 215 oc
10 mmØ 8 mmØ 10 mmØ
190 mm spacing 215 mm spacing 190 mm spacing 10mmØ 95
mm spacing
*note:the boxes in yellow should be inputed by the designer,while blue ones are computed by the program. =)
CARMEL B. SABADO CE-162 PROF. GERONIDES P. ANCOGBSCE-5 2nd Excel Program SEPT. 6, 2009*note:the boxes in yellow should be inputed by the designer,while blue ones are computed by the program. =)
****====DESIGN OF TWO-WAY SLAB====****
7.7 m
6.2 m
Estimate slab thickness based on code minimum thickness requirement.GIVEN: Trial depth, h:
20.7 MPa = 154.444 mm
414 MPa say 160 mm
23.6bar size = 12Live load = 6.65 kPa
6.2 m
7.7 m
Slab load:DL:
3.776 kPa
0.59 kPa
TOTAL = 4.366 kPaLL: 6.65 kPa
17.417 kPaSlab aspect ratio, m:
= 0.805194805
Positve moments:Case 4: w L
0.039 4.366 6.2 6.545
0.048 6.65 6.2 12.270
27.486
0.016 4.366 7.7 4.142
0.02 6.65 7.7 7.886
17.587
fc' =
fy =
wc = kN/m³mmφ
LA =
LB =
slab: wch =
finish, assume 25mm cement finish 0.025wc =
Ultimate load: wu = 1.4DL + 1.7LL =
coeff, c M=cwL²
Ma, pos DL
Ma, pos LL
Mau, pos = 1.2DL + 1.6LL
Mb, pos DL
Mb, posLL
Mbu, pos = 1.2DL + 1.6LL
h=2 ( A+B )180
m=LALB
Negative moments:
At continuous edge: L
0.071 17.4174 6.2 47.536 kN-m/m
0.029 17.4174 7.7 29.948 kN-m/m
9.162 kN-m/m
5.862 kN-m/m
Design of middle strip in the short direction:h d
Mu = Mmax = = 47.536 Kn-mTrial d = h - (20 + φ/2) = = 134 mm
= 2.941527733
= 0.002747419
= 0.016031805
= 0.007826 ok, use this rho!!!=)
= 113.0973355 mm2
= 1048.632079 mm2
= 107.8522561 mm oc
At mid-span:Mu = 27.486 Kn-mRu = 1.700853684p = 0.004328795 ok, use this rho!!!=)As = 580.0584963 mm2s = 194.9757417 mm oc
At discontinuous end:Mu = 9.162 Kn-mRu = 0.566951228p = 0.001392252 use pmin!!!=(As = 368.1540976 mm2s = 307.2010776 mm oc
Design od middle strip in the long direction:h d
Mu = 29.948 Kn-mdL = h - (20 + 1.5φ) = 122 mm
Ru = 2.235633472p = 0.005795189 ok, use this rho!!!=)Ao = 113.0973355 mm2As = 776.5553675 mm2
coeff, c wu M=cwL²
Ma, neg
Mb,neg
At discontinuous edge: M = 1/3(Mpos)
Ma, neg
Mb,neg
As = ρbd
Ru=M u /φ
bd2
ρmin=[ 1. 4f y,√ f c '4 f y ]min
ρmax=. 75[ . 85 f c ' β1
f y
. 003 Es
. 003 Es+ f y ]ρ= 1ω [1−√1−
2ωRuf y ]=. 85 f c '
f y [1−√1−2Ru
. 85 f c ' ]Ao=
π4Db2
s=1000 AoAs
s = 145.6397576 mm oc
At mid-span:Mu = 17.587 Kn-mRu = 1.312895778p = 0.00329931 ok, use this rho!!!=)As = 402.5158091 mm2s = 280.976133 mm oc
At discontinuous end:Mu = 5.862 Kn-mRu = 0.437631926p = 0.001070566 use pmin!!!=(As = 335.185074 mm2s = 337.4175771 mm oc
Check for shear:Total load on panel, Wt = LALBwu = 831.5067 Kn
= 0.71
= 38.3357 Kn/mShear concrete:
d = 134 mm
= 91.44948 shear is okay!!=)
SLAB DETAILS FOR BENDING OF REINFORCEMENTS
Short Direction:fixed bar spacing at mid-span, s = 150 mm oc
As(actual) = 1000Ao/s(fixed) = 753.9822 >As required at mid-span, ok As(required) = 580.0585
at exterior support Ap = As(actual)2/3 = 502.6548 >As required at exterior support,ok As(required) = 368.1541
at interior support Ap = As(actual)4/3 = 1005.31 <As required,provide extra bars As(required) = 1048.632 provide extra bars, n = 2
Ap = Ap + n(Ao) = 1231.504 >As required at interior support,ok
Long Direction:fixed bar spacing at mid-span, s = 220 mm oc
As(actual) = 1000Ao/s(fixed) = 514.0788 >As required at mid-span, ok As(required) = 402.5158
at exterior support Ap = As(actual)2/3 = 342.7192 >As required at exterior support,ok As(required) = 335.1851
at interior support Ap = As(actual)4/3 = 685.4384 <As required,provide extra bars As(required) = 776.5554 provide extra bars, n = 2 Ap = Ap + n(Ao) = 911.6331 >As required at interior support,ok
Shear per m of long beam, Case 4: CA
v A=CAWT
2 LB
V uc=φvc√ f c '
6bd
colu
mn
stri
p
provide 2 extra top bars
mid
dle
stri
pco
lum
n st
rip
provide 2 extra top bars
column strip middle strip column strip column strip
Slab thickness = 160 mm
Slab Details Scheme 2: Cutting of Reinforcements
colu
mn
stri
pco
lum
n st
rip
column strip middle strip column strip column strip
LB/4
12mmφ @150 oc bent 2/3
LB/2
12mmφ @ 220 oc bent 2/3
LB/4
LB/4
LA/4 LA/2 LA/4 LA/4
12φ top bars @ 245
LB/4
12φ
top
bars
@ 2
45
12φ
bot
bar
s @
175
12φ
top
bars
@ 1
05
12φ bot bars @ 250
LB/2
LB/4
12φ top bars @ 150
LB/4
LA/4 LA/2 LA/4 LA/4
Slab thickness = 160 mm
*note:the boxes in yellow should be inputed by the designer,while blue ones are computed by the program. =)
>As required at exterior support,ok
>As required at interior support,ok
>As required at exterior support,ok
>As required at interior support,ok