For a reinforced concrete section, the shape of shear stress diagram is
A. Wholly parabolic
B. Wholly rectangular
C. Parabolic above neutral axis and rectangular below neutral axis
D. Rectangular above neutral axis and parabolic below neutral axis
Answer: Option C

It is parabolic in the compression zone with zero at the top and maximum at the neutral axis. The value of shear-stress is constant in the tensile zone and is equal to the maximum shear-stress (q) because the concrete, below the neutral axis (tensile zone) is assumed to be cracked and neglected. The maximum value of shear stress (q) as per elastic theory is given by
q=Vbjd
where V = shear force at the section
b and d = dimensions of the section
j = Lever arm depth factor
How can explain with proff