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sigma_cbc=5//in MPa
sigma_st=230//in MPa
MF=1.4//modification factor
//let a be span to depth ratio
l=4.5//span, in m
a=MF*20
D=l*1000/a//in mm
D=160//approximately, in mm
//to calculate loading
self_weight=25*(D/10^3)//in kN/m
finish=1//in kN/m
partitions=1//in kN/m
live_load=4//in kN/m
W=self_weight+finish+partitions+live_load//total load, in kN/m
lef=l+D/1000//in m
M=W*lef^2/8//in kN-m
//check for depth
d=(M*10^6/(0.9*sigma_cbc/2*0.29*1000))^0.5//in mm
//assume 12 mm dia bars
D=d+12/2+15//in mm
//the calculated value of D is more than its assumed value
D=1.1*D//revised value of depth, in mm
D=250//assume, in mm
self_weight=25*(D/10^3)//in kN/m
finish=1//in kN/m
partitions=1//in kN/m
live_load=4//in kN/m
W=self_weight+finish+partitions+live_load//total load, in kN/m
lef=l+D/1000//in m
M=W*lef^2/8//in kN-m
//check for depth
d=round((M*10^6/(0.9*sigma_cbc/2*0.29*1000))^0.5)//in mm
D=d+12/2+15//in mm
D=250//approximately, in mm
Ast=round(M*10^6/(sigma_st*0.9*d))//in sq mm
s1=1000*0.785*12^2/Ast//which is less than 3d= 690 mm
s1=155//approximately, in mm
pt=Ast/1000/d*100//in %
Ads=0.12/100*1000*D//distribution steel, in sq mm
//assume 8 mm dia bars
s2=1000*0.785*8^2/Ads//which is less than 5d= 1150 mm
s2=165//approximately, in mm
//to calculate development length
w=0.23//support width, in m
l=l+w//in m
R=W*l/2//reaction at support, in kN
M1=R*w/2-W*w^2/2//bending moment at the face of wall, in kN-m
sigma_st=M1*10^6/(Ast/2*0.9*d)//in MPa
Tbd=0.6//in MPa
Ld=12*sigma_st/(4*Tbd)//in mm
La=w*1000-25//available length for bar over wall, which is greater than development length
//check for shear
V=W*lef/2//in kN
Tv=V*10^3/(1000*d)//in MPa
Tc=0.2212//permissible shear in concrete for p=0.315 and M15, in MPa
Tc=1.15*Tc//permissible shear for slabs, in MPa
//Tc>Tv; hence no shear reinforcement is required
mprintf("Summary of design\nSlab thickness=%d mm\nCover=15 mm\nMain steel = 12 dia @ %d mm c/c\nAlternate bars are bent up at 45-degree at support at a distance of l/7 from support face\nDistribution steel=8 dia @ %d mm c/c",D,s1,s2)
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