Abstract
Initial distortion and residual stress are well known as the most important initial imperfection factors and have a significant effect in the decreasing on compression ultimate strength of thin walled structures. The present work focuses on influence of initial imperfection factors to ultimate strength of steel columns especially for welded box section compression members. Beam and developed shell Finite Element (FE) models are used under compression loading. The result comparison between FE model's and ultimate strength formulations in some specifications are used to measure the result accuracy and accomodate the ultimate strength formulations of bridge specifications according to the behavior of current steel compression members. Result of analytical study indicates that both FE models have good similarities with the formulations that have stated in specifications especially JSHB 2012 which means that the specifications have good capability in illustrating behavior of steel compression members.
