Question

The most economical central angle of the arch rings of an arch dam can be adopted only at one place preferably at mid-height in an arch dam is of the type __________________

(a) constant angle arch dam

(b) constant radius arch dam

(c) both constant angle and constant radius arch dam

(d) variable radius arch dam

The question was asked in a dream while sleeping

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

Answer 1

The correct answer is (b) constant radius arch dam

To explain: The most economical central angle is equal to 1330-34’ and such an angle can be adopted only at one place in constant radius arch dam since as there is considerable variation with height due to narrow V-shape of the valley. It is therefore considered to keep the economical angle of 1330-34’ at about mid-height and the angle at the top will be more than this value due to topographical conditions.