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.
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
Neutral axis can be calculated by equalling moment of area from both parts as shown below
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
flexural stress for tension zone. y at extreme tension equal 12.08in=1.0067ft