Earthquake Engineering MCQ with answer and solution

Concept

Conditions requiring vertical earthquake effect consideration

Formula

IS 1893 (Part 1): 2016 Amendment No. 2

Step-by-step solution

1. Vertical earthquake shaking produces significant fluctuating axial forces and flexural demands on horizontal and irregular members. 2. Amendment No. 2 expands the scope of mandatory vertical shaking considerations beyond basic structures. 3. It stipulates consideration for structures in high seismic zones (IV and V), irregular structures, soft soils, long spans, cantilevers, and prestressed components. 4. Therefore, option C comprehensively describes all mandated conditions. Answer: C

Explanation

As per Amendment No. 2 to IS 1893 (Part 1): 2016, vertical seismic effects must be explicitly evaluated for structures in Seismic Zones IV and V, structures with horizontal or vertical irregularities, structures resting on soft soil, or those with long spans, large cantilevers, or prestressed members.

Why the other options are wrong

A) Zone III alone does not trigger mandatory vertical shaking checks unless specific structural triggers apply. B) Soft soil alone is only one of multiple triggering conditions. D) Prestressed structures are only one category among several requiring vertical analysis.

Shortcut

Vertical shaking = Zones IV/V, irregular plans, soft soils, cantilevers, long spans, and prestressed elements.

Common mistake

Believing vertical earthquake shaking is only evaluated in prestressed structures.