Behavior and Design of Steel Delta Girders for Flexure and Shear

A steel delta girder (SDG) is formed by welding two inclined plates in the form of a V from the web to the compression flange of an I-section. Analytical, numerical, and experimental research on SDGs has shown that they possess enhanced flexural and shear capacities over traditional I-sections with comparable cross-sectional areas. In this paper, three-dimensional nonlinear inelastic finite-element models that take into consideration the effects of initial geometrical imperfections and residual stresses are developed to investigate the inelastic lateral-torsional buckling and shear behavior of simply-supported SDGs under uniform bending and pure shear. Using European H- and I-sections as base cross sections, the analyses cover a wide range of SDG dimensions and inclined stiffener configurations. The results of these analyses demonstrate that the flexural capacities of SDGs can be represented by two of the existing EuroCode 3 (EC3) buckling curves. Design equations for the shear capacity of SDGs are then developed and proposed in accordance with EC3 provisions. Finally, design recommendations for selecting the proper inclined plate dimensions and configurations within the delta region of SDGs are provided.