Current American steel building and bridge design specifications (AISC 1999, AASHTO 1998) simplify the flexural design of both homogeneous and hybrid I-shaped members by treating local and global inelastic stability phenomenon independently. According to both specifications, if a homogeneous or hybrid section is compact and sufficiently braced against lateral instability, the member will achieve or exceed its theoretical plastic moment capacity and maintain this capacity so as to allow sufficient rotation capacity for inelastic force redistribution to take place (Yura et al. 1978). Treating local and global buckling independently has been proven by past experience to be successful when formulating flexural design provisions for lower strength steels. However, new research (Earls 1999, 2000a, 2000b, 2001) is proving that this approach is much more difficult to apply to the design of High Performance Steel (HPS) I-shaped flexural members. The main objective of the current study is to investigate the effect HPS flanges have on hybrid girder flexural ductility. Finite element models of hybrid HPS girders, employing nonlinear shell elements, are used to study the influence of flange slenderness ratios, and bracing configuration on hybrid HPS girder response at ultimate
