Working Stress Method MCQ with answer and solution

Concept

Cantilever action height in circular tanks

Formula

h = H/3 or 1 m (whichever is more)

Step-by-step solution

1. In circular water tanks fixed at the base, the lower portion exhibits cantilever action while the upper portion resists pressure mainly by hoop tension. 2. The height h above the base up to which cantilever action is assumed to exist depends on the overall height H of the tank. 3. According to standard design practice, h is taken as H/3 or 1 m, whichever value is larger. Answer: D

Explanation

In circular water tanks with a rigid base, the lower wall section resists hydrostatic pressure primarily through cantilever bending action. Design standards state that this cantilever effect extends from the base up to a height equal to H/3 or 1 m, whichever is greater. Above this height, ring tension becomes the primary load-resisting mechanism in the wall.

Why the other options are wrong

A) Taking full height H overestimates the specific base region governed by cantilever action. B) H/3 alone fails to consider the fixed 1 m lower limit for cantilever action. C) 1 m alone ignores deep tanks where H/3 is greater than 1 m.

Shortcut

Circular tank base cantilever height h = H/3 or 1 m, whichever is greater.

Common mistake

Selecting H/3 or 1 m individually without considering the requirement of taking whichever value is greater.