Design of Beams MCQ with answer and solution

Concept

Web crippling is local yielding or crushing of the thin web near the flange, just below a point load or over a support.

Formula

Web bearing capacity F_w = (b₁ + n₂) × t_w × f_yw / γ_m0, where n₂ = 2.5 × (t_f + r) spread

Step-by-step solution

1. A heavy point load or support reaction acts on the flange of a beam. 2. The load spreads into the thin web over a short length near the root of the flange. 3. High compressive stress in this small area makes the web yield or crush locally. 4. This local failure under point loads is called web crippling. So the answer is (B).

Explanation

Web crippling is a local failure of the web under concentrated loads or reactions. The web crushes near the flange-web junction. Bearing stiffeners or longer stiff bearing are used to prevent it.

Why the other options are wrong

(A) Excessive bending moment causes flexural or lateral-torsional failure, not crippling. (C) Reduced flange width affects local flange buckling and lateral stability. (D) Column action of the web describes web buckling, not web crippling.

Shortcut

Crippling = crushing near the flange under a point load. Buckling = column action of the web.

Common mistake

Students confuse web crippling (local crushing) with web buckling (column action of the web).