Nonlinear Analysis of Composite Steel Girder Bridges

This paper describes a procedure for the nonlinear analysis of composite steel girder highway bridges. The procedure uses a modified grillage (grid) analysis method where material nonlinearity is modeled by empirically derived moment-curvature relationships. These are obtained from experimental data on the behavior of typical composite steel girder bridges. A linear variation of plastic curvature along the length of each beam element is assumed. An equivalent grid plastic hinge length is used to simulate the extent of plastification over the whole length of a grid element. The procedure can account for span continuity by including a negative bending moment curvature relationship. Numerical investigations verify the proposed method's validity by comparing the analytical results with those of in-situ and laboratory full-scale and model-scale bridge tests. This paper also demonstrates that the proposed nonlinear analysis method provides a simple tool that can be used to obtain reasonably accurate representations of the nonlinear behavior of composite steel girder bridges. The method uses a grillage discretization technique whose results are relatively insensitive to variations in the mesh size. The proposed method has a high potential for use in engineering practice because of the simple input requirements and its reasonable level of accuracy.