Question 1

What is the difference between moment and shear?

Accepted Answer

Bending moment causes a beam to flex — it controls the required depth and reinforcement at the section. Shear force causes internal sliding — it controls stirrup/shear reinforcement requirements. Moment is usually maximum at midspan for uniform loads, while shear is maximum at the supports.

Question 2

When should I use a fixed beam instead of simply supported?

Accepted Answer

Fixed beams have lower maximum moment (wL²/12 vs wL²/8) and deflection, allowing smaller sections. However, they require moment connections at supports, which are more expensive to construct. Simply supported beams are simpler and more common in practice.