Question

Outer curve of an arch is called -

• A. Intrados
• B. Evolute
• C. Involute
• D. Extrados

Hint:

In arch design, always distinguish between the intrados and extrados for understanding stress distribution.

Answer 1

The Correct Option is D

Step 1: Understanding arch terminology.
The outer curve of an arch, which is subjected to tensile forces, is known as the extrados. This is the counterpart to the intrados, which is the inner curve of the arch.

Step 2: Analyzing the options.
(A) Intrados: Intrados is the inner curve of the arch, not the outer curve.
(B) Evolute: Evolute refers to a curve derived from the envelope of tangents to another curve, unrelated to the outer curve of an arch.
(C) Involute: Involute is a term used for a curve generated by a point on the end of a string unwinding from another curve, not related to arches.
(D) Extrados: Correct — The extrados is the outer curve of the arch, which carries the compressive forces.

Step 3: Conclusion.
The correct answer is (D) Extrados, as it is the outer curve of an arch.