Flexural strength of hollow tubular flange plate girders with slender stiffened webs under mid-span concentrated loads: Fid-Bau Portal

Flexural strength of hollow tubular flange plate girders with slender stiffened webs under mid-span concentrated loads

Hassanein, M.F. / Kharoob, O.F.

Abstract A three-dimensional elastic finite element (FE) model, considering merely the geometric nonlinearity, is used in the first part of this paper to study the overall buckling resistance of hollow tubular flange plate girders (HTFPGs). Modeling is conducted using the general-purpose FE software package ABAQUS under mid-span concentrated loads. The developed model consists of the type and number of elements that allows capturing the different possible buckling mode patterns including local, interactive and lateral-torsional buckling. Finite element results revealed that, unlike the case of conventional beams with solid webs, the moment-gradient factor $C_{b}$ is significantly influenced by the girder geometry and slenderness. Hence, an equation representing the $C_{b}$ factor for the case of HTFPGs with slender stiffened webs is proposed. The paper extends to investigate the nonlinear flexural strengths of such girders. The results are compared to the AISC predictions. The original AISC predictions are found to be highly conservative using the code recommended $C_{b}$ value as well as the current proposed value. However, the suggested AISC strength (found in Hassanein et al., 2013 [1]) using $C_{b} = 1.35$ is found to be the best among other values but it suffers from the discontinuity in the flexural strength-unbraced length relationship. Accordingly, a line representing the middle part of this relationship is currently assumed. Comparisons with FE results indicate that the currently proposed AISC method can fairly predict the flexural strength of the HTFPGs with slender stiffened webs.

Highlights • A FE model for HTFPGs under mid-span concentrated loading is presented. • A formula for the moment-gradient factor is provided for the case of HTFPGs. • The AISC predictions are highly conservative for the HTFPGs. • The proposed design model is shown to predict well the strengths of the HTFPGs.