Flexural stress calculation using transformed area method for rectangular beam

assume the section for beam shown in figure 1 cracked calculate the flexural stresses for the given load or moment using transformed area method.

transform2barea2bex2b1-8930483first, we will calculate the transformed area of steel. the concrete below the neutral axis will not contribute in resisting of tension. figure 2 shows the section after transformation  Transformed area=As*n=8*1.76=14.08in2 t-aaaa_-9502790Neutral axis can be calculated by equalling moment of area from both parts as shown below  14.08*(17-x)=(x/2)*(14*x) moment of inertia for transformed section =(14*4.92^3)/12+4.92*14*2.46^2+14.08*12.08^2=2610.422in4=0.125886ft4 flexural stress for compression zone. y at extreme compression equal 4.92in=0.41ft fc=60*0.41/0.125886=195.414k/ft2=1357psi flexural stress for tension zone. y at extreme tension equal 12.08in=1.0067ft ft=(8*60*1.0067/0.125886)=3838.392k/ft2=26655.49psi