Fundamental behaviour of concrete-filled pentagonal flange plate girders under shear

Hollow tubular flange plate girders are found to possess higher flexural and shear strengths over those of I-section plate girders with flat flanges. Recently, concrete-filled pentagonal flange girders (CFPFGs) have been suggested in literature to increase the out-of-plane flexural strength of the girders. The geometrical configuration of the section is assumed identical to that of the girder with the rectangular concrete-filled flanges, but the flange depth-to-width ratio is designed to be larger in order to reduce the local buckling of the web. In this paper, the fundamental shear behaviour of these CFPFGs with slender stiffened webs is investigated. Nonlinear three-dimensional finite element (FE) analyses using ABAQUS are employed to conduct parametric studies, having first validated the models against available experimental data. For comparison purposes and to examine the effect of the infill concrete, steel pentagonal flange girders (SPTGs) are also generated. It is found that CFPFGs and SPFGs with the same dimensions have similar buckling shapes but with different loads with the buckling load of the CFPFG being higher than that of the corresponding SPFG. In the post-buckling stage, the width of the inclined tension field becomes greater in the CFPFGs relative to that of the SPFGs. This highlights the influence of the infill concrete which increases the stiffness of the upper flanges, and hence allows the webs to carry additional shear loads compared to SPFGs. Several affecting parameters are, additionally, examined and important conclusions are remarked. The FE strengths are compared with the design strength of the webs following the EN 1993-1-5, indicating that it can conservatively be used with the SFPGs. On the other hand, it becomes highly conservative for the CFPFGs. (C) 2015 Elsevier Ltd. All rights reserved.