Question

Which of the following assumptions is not an ideal beam behaviour?

(a) local and lateral instabilities of beam are prevented

(b) any form of local buckling is prevented

(c) compression flange of beam is restrained from moving laterally

(d) compression flange of beam is not restrained from moving laterally

I got this question in a national level competition.

The above asked question is from Lateral Stability of Beams in portion Design of Beams of Design of Steel Structures

Answer 1

Right option is (d) compression flange of beam is not restrained from moving laterally

To elaborate: Two important assumptions are made to achieve ideal beam behaviour: (i) compression flange of beam is restrained from moving laterally, (ii) any form of local buckling is prevented. A beam loaded predominantly in flexure would attain its full moment capacity if local and lateral instabilities of beam are prevented.