Research On Flexural Behavior Of Hybrid HPS Girders

High performance steel has a good improvement on strength, weld ability, weather-resistant, toughness and fatigue-resistant, and it has a bright prospect of using in large-span bridges and high buildings. Bridges built and under construction in American not only use high performance steel, but also use hybrid design. That means different steels are used in flanges and webs for the purpose of economy.This article takes HPS 70W as the basic material used in research, which is included in American code ASTM A709. Nonlinear finite element models are used to study flexural behavior of hybrid HPS girders and homogeneous HPS girders.In the theoretical part, the concept of hybrid design and the advantages of its use in HPS girders are expatiated. The definition and calculation method of rotation capacity are introduced from American code. By describing two different failure modes of HPS girders, two optimal lateral bracing configurations in plastic hinge section area of HPS girders are provided according to foreign literature.In the computing part, finite element models of ANSYS are built and verification work is done by comparing with experimental data. Three groups of hybrid HPS girders and three groups of homogeneous HPS girders are calculated using nonlinear elastoplastic method. On the basis of rotation capacity, failure mode and ultimate load, the influence of flange slenderness ratios and bracing configuration on flexural behavior are studied. The conclusion that placing lateral bracing a distance of d or d/2 on either side of the mid-span can provide considerable improvement in rotation capacity of HPS girders in foreign literature is verified. Compared with the steel code of our country, suggested value of flange slenderness ratio is given.