Question

In which of the following cases are castellated beam desirable?

(a) when more span to be covered than rolled section

(b) when beam subjected to substantial concentrated loads

(c) when beam to be used as continuous beam

(d) when higher fire resistance than rolled section required

The question was asked in class test.

Query is from Castellated Beams & Lintels topic in division Design of Beams of Design of Steel Structures

Answer 1

Correct answer is (a) when more span to be covered than rolled section

Easy explanation: The section of castellated beam will have more depth and section modulus than original rolled section. This allows the beam to span further than parent rolled section. Castellated beams may not be desirable when beam is subjected to substantial concentrated loads, or when castellated beam is used as a continuous beam across several supports. Castellated beams are less attractive when very high requirements for fire resistance are required because the fire resistant coating has to be around 20% thicker than for rolled sections in order to obtain the same fire resistance as rolled section.