Calculate the nominal flexural strength of the beam sections

Calculate the nominal flexural strength of the beam sections shown below. Given: fy= 60,000 psi andf,c= 5,000 psi, As = 4 in2 10 in. 12 in.

Solution

The steel will be in tension

Grade of steel = 60 ksi

grade of concrete=5 ksi

Area of steel = 4 in²

Let the compression zone depth be \'a\'

0.85*5*12*a=0.9*4*60

a=4.23 in

Effective depth = 18-2.5=15.5 in

lever arm length = 15.5-4.23/2=13.38 in=1.15 ft

Moment capapcity = 0.75*0.9*4*60*1.15=18.66 kip-ft