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