It is in one of the settings in Analysis Options. In my case, the utilizations in beams are changed drastically when I change the option from ON to OFF or vice versa. Which is the correct setting to use?
Shear deformation effect shown in option card will be followed Timoshenko beam theory
They have 2 beam theories which is Euler-bernoulli and Timoshenko. Normally, most of people will known Euler-bernoulli (Classic Beam Theory) which assume 'section remain plane when it is bended'.
Timoshenko beam theory will count this part into bending moment calculation. You will see that we have to give 'shear stiffness properties' when we try to calculate bending moment of the beam in Timoshenko formular while it is do not needed in classic beam theory.
This shear effect will give little effect in thin and long beam while it will significant in 'thick and short beam.