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Example 5: nominal moment for reinforced concrete T beam with wider web at bottom

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Determine Mn for beam in figure 1.if fy= 60,000 psi and f c'= 4000 psi.
\
Figure 1








assuming a<4in
T=C
As*fy=0.85*fc'*a*b
6*0.79*60,000=0.85*4000*a*34
a=2.46in 
assumpition is ok


Mn=As*fy*(d-a/2)
Mn=4.74*60,000*(19-2.46/2)
Mn=5053788lb-in=421.15K-ft

Figure 2


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