Influence Line Diagrams MCQ with answer and solution

Concept

Loading condition for influence line diagrams

Formula

NONE

Step-by-step solution

1. An Influence Line Diagram (ILD) represents the variation of a structural response at a specific section. 2. It is plotted as a dimensionless unit load moves across the span of the structure. 3. Therefore, ILD is specifically drawn for a moving unit load. Answer: C

Explanation

An influence line diagram graphically represents how internal forces, reactions, or deflections at a specific location in a structure change as a single unit load moves across the span. Because it evaluates structural response due to load position rather than static load values, it is drawn for a moving unit load.

Why the other options are wrong

A) Influence line diagrams represent response variation due to a moving load, not fixed static loading. B) The load must be moving across the span, not stationary at a static position. D) Option C is the correct answer.

Shortcut

Influence Line Diagram (ILD) is always drawn for a Moving Unit Load.

Common mistake

Confusing influence line diagrams (drawn for a moving unit load) with static load bending moment and shear force diagrams.