Ultimate strength of box section steel bridge compression members in comparison with specifications

• We focus on the ultimate strength of box section steel compression members.
• We observe the effects of slenderness and initial distortion to the member strength.
• Models have good agreement with JSHB 2012 and AISC 2005/AASHTO 2010 design strength.
• Ultimate strength decreases as slenderness and initial distortion increase.
• Local buckling occurs in the members with small slenderness.

Initial distortion and residual stress are well known as the most important initial imperfection factors and have a significant effect in decreasing the ultimate strength of compression members. The present work focuses on predicting the ultimate strength of welded box section steel compression members regarding initial imperfection factors. Beam compared with shell type of Finite Element (FE) models varied in slenderness ratio and initial distortion are used to assess the accuracy of present numerical results. The comparison of result between FE models and design strength formulations in some specifications are used to assess the ultimate strength formulations of bridge specifications according to the behavior of current steel compression members. It can be observed from numerical results that FE models and design strength by JSHB 2012 and AISC 2005/AASHTO 2010 have good agreement each other which means that the specifications have good capability in assessing the ultimate strength of steel compression members. Parametric study of the ultimate strain varied in slenderness ratio and load versus displacement curves of compression members are also introduced in order to perform more detail steel columns displacement behaviour. Finally, present work proposed a flowchart in designing steel compression members with the expectation that it will be helpful as reference for researchers and engineers in practical fields.