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Check of Punching Shear in Flat Slabs and Rafts under N, Mx, and My According to ACI 318-02
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For Interior Rectangular Columns (4 sides only)
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Building:part6Column:c81-80-95-84
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Slab
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Slab thickness =250mm
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Top cover to rebar =25mmdiameter of rft =10
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d =220mm
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Straining Actions
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Un-balanced Moment
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Mu1 (perp.) =0KN.m
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Mu2 (parllel) =0KN.m
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Ultimate Shear force (Vu) =
2400KN
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Column Dimensions:
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LONG SIDE OF COLUMN
C1=500mm
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SHORT SIDE OF COLUMN
C2=500mmbc=1,0=C1/C2
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as=40
(20 for corner, 30 for edge and 40 for interior col)
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edge distance (e)=
5000mm
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Materials
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Slab Concrete Grade (Fcu)=
30Mpa
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Fc'=0.80*Fcu =
24Mpa
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Reinforcement Steel Grade=
450Mpa
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Critical section in punching:
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b1=720mm
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b2=720mm
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bo= 2b1 +2b2 =
2880mm
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Flexural portion of moment (gf)1=
0,60
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Eccentric shear portion (gv)1=
0,40
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Flexural portion of moment (gf)2=
0,60
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Eccentric shear portion (gv)2=
0,40
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Shear/Torsion Parameters
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Shear/Torsion resisting Parameters according to ACI318-02, R11.12.6.3
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c=b1/2=360mm
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c'= b1-c=360mm
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Ac=0,6336m2
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Bending normal to edge:
Jcn=0,0560m4
Jcn=[b1d*(b1+3b2)+d^3]*c/3
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Bending Parllel to edge:
Jcp=0,0560m4
Jcp=b2/2*(b2*d(b2+3b1)+d^3)/3
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from "Notes on ACI318-02, pp 16-16"
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Ultimate Shear Stress
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Ultimate shear force
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V/A=3787,879
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(γv)1*Mu1*c/Jcn=
0,000
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(γv)1*Mu1*c'/Jcn=
0,000
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(γv)2*Mu2*b2/2/Jcp=
0,000
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Critical Ultimate shear stress =
3787,879Kpa
Inner corner=Vu/Ac+gv Mu1(perp)*c/Jcn + gv Mu2(parallel)*(b2/2)/Jcp
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Concrete Punching Strength:
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f =0,75
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fvc (1)=1837,117Kpa
Equation 11-35
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fvc (2)=1569,204Kpa
Equation 11-36
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fvc (3)=1224,745Kpa
Equation 11-37
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fvc (min)=1224,745Kpa
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Is (vu )less than fvc (min) ?
No, NEED SHEAR RFT, PLEASE CARRY ON
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CALCULATION OF REQUIRED SHEAR REINFORCEMENT
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Shear force in reinforcement
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Check if (vu) is less than (f 6 sqrt(fc') ) or not
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vu=3787,879Kpaf 6 sqrt(fc')=1837,117Kpa
No, increase slab thickness
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f vc (for punching RFT=2SQRT(fc')=
612,372Kpa
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Shear force to be resisted by reinforcement
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Vs=bo d *(vu-fvc)=
2012,001KN
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Check if (Vs) is less than (f 4 sqrt(f'c)*bo d ) or not
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f 4 sqrt(f'c)*bo d =
776,00KNFALSE
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Required Reinforcement
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Total area of steel on four sides of column is given by
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Av = Vs * S / (f *fy *d)
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Stirrups Spacing (s) =
70mm
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number of legs =
4
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Av =0,001896835794m2 =1896,84mm2
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Av/Side =474,209mm2
Then use, Vl U-bars T
13@70
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Distribution of shear RFT
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Determination of distance from column face for termination of stirrups
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stirrups are not required when, Vu is less than f vc (min) bo'*d
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then, bo'=17814,47mm
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bo'= 2C1 +2 C2 + 4 a Sqrt(2),
where a is the extension of shear RFT from face of column
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a = (bo'-2C1-2C2)/4Sqrt(2)
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a = 2795,63mm
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Design Report
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USE THE FOLLOWING SHEAR REINFORCEMENT AT EACH SIDE OF COLUMN
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use RFT of T13@704legs
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for a distance 2800mm
from each side of support
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