Behavior of high-strength steel welded rectangular section beam–columns with slender webs

Abstract

This paper develops a double nonlinear finite element model that can take account of both geometric and material imperfections. On verified the numerical model the behavior and ultimate carrying capacity of eccentrically loaded welded thin-webbed rectangular section columns made from high strength steel with a nominal yield stress of 460MPa are analyzed, and further the influences of the slenderness ratio, web depth-to-thickness ratio, flange width-to-thickness ratio, and relative eccentricity ratio on the ultimate carrying capacity are investigated. On the basis of these, the simple calculation formulas, which use the gross cross-section properties, for predicting the in-plane maximum strength of high strength steel beam–columns with large depth-to-thickness ratios are proposed. It shows that the developed finite element model can simulate the local–overall interaction buckling behavior of the eccentrically loaded welded box-section compression members. A brittle failure characteristic is found with a relatively steeper drop just after the peak in the load–displacement curve. A nonlinear and complex stress distribution, in the longitudinal direction, when reaching the ultimate capacity, seriously deviates from an elastic stress distribution, on the basis of which, the effective width is determined. The non-dimensional ultimate bearing capacity is approximately linear with the slenderness, depth-to-thickness ratio and width-to-thickness ratio, respectively. The interaction curves between the axial force and flexural moment for the high-strength steel thin-webbed rectangular section beam–columns are nearly linear. After introducing a steel yield strength modification factor, the formula based on the edge fiber yielding criterion can precisely predict the local–overall interactive buckling strength of high strength steel beam–columns.