Question

The value of fcr,b is given by

(a) fcr,b = [1.1π^2E/(LLT/ry)^2]{1+1/20[(LLT/ry)/(hf/tf)]^2}

(b) fcr,b = [1.1π^2E/(LLT/ry)]{1-1/20[(LLT/ry)/(hf/tf)]}

(c) fcr,b = [1.1π^2E/(LLT/ry)^2]{1+1/20[(LLT/ry)/(hf/tf)]^2}^0.5

(d) fcr,b = [1.1π^2E/(LLT/ry)^2]{1-1/20[(LLT/ry)/(hf/tf)]^2}^0.5

This question was addressed to me by my college director while I was bunking the class.

Query is from Design Strength of Laterally Unsupported Beams in section Design of Beams of Design of Steel Structures

Answer 1

Correct choice is (c) fcr,b = [1.1π^2E/(LLT/ry)^2]{1+1/20[(LLT/ry)/(hf/tf)]^2}^0.5

The explanation is: The value of fcr,b is given by fcr,b = [1.1π^2E/(LLT/ry)^2]{1+1/20[(LLT/ry)/(hf/tf)]^2}^0.5, where ry = radius of gyration about weaker axis, LLT = effective length for lateral-torsional buckling, tf = thickness of flange, hf = centre-to-centre distance between flanges.