Flexural Resistance of Longitudinally Stiffened I-Girders. II: LTB and FLB Limit States

AbstractThe current AASHTO specifications impose a penalty on the strengths corresponding to the compression flange in slender-web cross sections due to bend-buckling of the web in flexural compression. This web bend-buckling factor (Rb) does not account for any potential benefits from the influence of web longitudinal stiffening. In a companion paper, the authors developed a cross-section model that can be used to estimate the flexural capacity of I-girders at the yield limit state. In this paper, an improved handling of combined web bend-buckling and lateral torsional buckling (LTB) of longitudinally stiffened I-girders is proposed based on finite-element test simulations. Results from the proposed prediction model are compared to available experimental tests. In addition, the Rb calculated from the proposed model, used in conjunction with the current specification flange local buckling (FLB) equations, is shown to provide an improved characterization of the FLB capacity of these types of members.