Question

The stresses due to rib-shortening become quite important in the case of _____________

(a) long thin arch dams

(b) thick arch dams of small angle

(c) both thin and thick arch dams

(d) all types of arch dams

The question was asked in a job interview.

The above asked question is from Arch Dams topic in portion Arch and Buttress Dams of Irrigation Engineering

Answer 1

Correct choice is (b) thick arch dams of small angle

To elaborate: In the case of an arch dam, the ends being fixed the distance between them does not change and this restriction of the change in the span causes additional stresses known as rib-shortening stresses. These stresses are small in a long thin arch but in the case of a thick arch of small-angle, they are appreciable.