Working Stress Method MCQ with answer and solution

Concept

Allowable stress philosophy in working stress design

Formula

σ ≤ σ_permissible = f_y / FOS

Step-by-step solution

1. Working Stress Method (WSM) assumes linear elastic behavior of both concrete and steel under service loads. 2. Service loads are applied without load factors. 3. Structural safety is ensured by keeping working stresses below allowable (permissible) stresses. 4. Thus, design in the working stress method is based on allowable stresses. Answer: C

Explanation

The Working Stress Method is an elastic design philosophy where structural members are proportioned such that internal stresses under service loads do not exceed allowable (permissible) stresses. Permissible stresses are established by applying a factor of safety to material yield or ultimate strength.

Why the other options are wrong

A) Ultimate loads are used in ultimate load and limit state methods. B) Partial safety factors are characteristic of limit state design. D) Collapse loads are used in plastic analysis and limit analysis.

Shortcut

Working Stress Method = Service loads + Allowable stresses; Limit State Method = Factored loads + Design strengths.

Common mistake

Confusing WSM with Limit State Method, which designs for ultimate loads and uses partial safety factors.