l=1//span, in m t=0.27//tread in m sigma_cbc=5//in MPa sigma_st=140//in MPa MF=1.6 a=MF*7 D=l*10^3/a//in mm D=100//assume, in mm W1=D/10^3*t*25//in kN/m M1=W1*l/2//in kN-m M2=t*3*l/2//in kN-m M3=1.3*l//in kN-m M=M1+max(M2,M3)//in kN-m d=sqrt(M*10^6/0.87/t/10^3)//in mm d=83//in mm //assume 8 mm dia bars dia=8//in mm D=d+dia/2+15//this is slightly more than assumed value, hence OK D=100//in mm z=0.87*d//in mm Ast=M*10^6/sigma_st/z//in sq mm n=Ast/0.785/8^2 n=4//assume Ads=0.15/100*D*t*10^3//distribution steel, in sq mm //provide 6 mm dia bars s=1000*0.785*6^2/Ads//>5d=415 mm s=415//in mm Tbd=0.6//in MPa Ld=dia*sigma_st/4/Tbd//in mm Ld=470//assume, in mm mprintf("Summary of design\nThickness of steps=%d mm\nCover from top=15 mm\nMain steel = 8 mm dia, %d in each step with development length of %d mm\nDistribution steel = 6 mm dia @ %d mm c/c",D,n,Ld,s)