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+fck=15//in MPa
+fy=415//in MPa
+phi=30//angle of repose, in degrees
+H=5//height of wall, in m
+B=0.6*H//assume, in m
+T=B/4//assume toe to base ratio as 1:4, in m
+W=16//density of retained earth, in kN/cu m
+Wu=1.5*W//factored load, in kN/cu m
+P=Wu*H^2/2*(1-sind(phi))/(1+sind(phi))//in kN
+M1=P*H/3//in kN-m
+M1=167//round-off, in kN-m
+//bending moment at 2.5 m below the top
+h=2.5//in m
+M2=Wu*h^2/2*(1-sind(phi))/(1+sind(phi))*h/3//in kN-m
+M2=21//round-off, in kN-m
+//thickness of stem (at the base)
+d=sqrt(M1*10^6/0.138/fck/1000)//in mm
+d=285//round-off, in mm
+dia=20//assume 20 mm dia bars
+D1=d+dia/2+25//in mm
+D2=200//thickness at top, in mm
+D3=D2+(D1-D2)*h/H//thickness at 2.5 m below top, in mm
+d3=sqrt(M2*10^6/0.138/fck/1000)//in mm
+D3=d3+dia/2+25//< 260 mm (provided), hence OK
+D3=260//in mm
+d3=D3-dia/2-25//in mm
+//main steel
+//(a) 5 m below the top
+//Xu=0.87*fy*Ast/0.36/fck/b = a*Ast
+a=0.87*fy/0.36/fck/10^3
+//using Mu=0.87 fy Ast (d-0.416 Xu), we get a quadratic equation
+p=0.87*fy*0.416*a
+q=-0.87*fy*d
+r=M1*10^6
+Ast=(-q-sqrt(q^2-4*p*r))/2/p//in sq mm
+pt=Ast/1000/d*100//in %
+//provide 20 mm dia bars
+s1=1000*0.785*20^2/Ast//in mm
+s1=155//round-off, in mm
+//(b) 2.5 m below the top
+//Xu=0.87*fy*Ast/0.36/fck/b = a*Ast
+a=0.87*fy/0.36/fck/10^3
+//using Mu=0.87 fy Ast (d-0.416 Xu), we get a quadratic equation
+p=0.87*fy*0.416*a
+q=-0.87*fy*d3
+r=M2*10^6
+Ast=(-q-sqrt(q^2-4*p*r))/2/p//in sq mm
+Astmin=0.12/100*10^3*D3//in sq mm
+Ast=max(Ast,Astmin)//in sq mm
+//provide 12 mm dia bars
+s2=1000*0.785*12^2/Ast//in mm
+s2=360//round-off, in mm
+//distribution steel
+Ads=0.12/100*10^3*D3//in sq mm
+//provide 8 mm dia bars
+s3=1000*0.785*8^2/Ads//in mm
+s3=160//round-off, in mm
+//check for shear
+Vu=P//in kN
+Tv=Vu*10^3/10^3/d//in MPa
+//for M15 grade concrete and pt=0.71
+Tc=0.54//in MPa
+//as Tc > Tv, no shear reinforcement required
+//development length
+//(a) At the base of stem
+dia=20//in mm
+Tbd=1.6//in MPa
+Ld=dia*0.87*fy/4/Tbd//in mm
+Ld=1130//round-off, in mm
+//(b) At 2.5 m below the top
+dia=12//in mm
+Ld=dia*0.87*fy/4/Tbd//in mm
+Ld=680//round-off, in mm
+mprintf("Summary of design:\nThickness of stem (at base) = %d mm\nThickness of stem at top = %d mm\nRefer Fig. 19.10 of textbook for reinforcement details",D1,D2)