Lateral Torsional Buckling Strength of Tubular Flange Girders

Abstract

I-shaped steel girders with tubular flanges have been studied for application in highway bridges because of their large lateral torsional buckling (LTB) strength relative to conventional I-shaped steel plate girders. This paper discusses the LTB strength of tubular flange girders, focusing on concrete-filled tubular flange girders (CFTFGs) where the concrete-filled tube is the compression flange. Using finite-element (FE) models of CFTFGs, a parametric study was conducted to investigate the influence of girder geometry and material strength on the LTB strength. Design flexural strength formulas, considering LTB, for construction conditions and for ultimate strength in the final constructed condition, were developed based on the results of the parametric study. These formulas estimate the LTB strength of CFTFGs that are perfectly braced laterally and torsionally at brace points. A similar FE study of conventional I-girders was conducted and the results are compared with those of CFTFGs.