Analytical Modeling of Nonlinear Behavior of Composite Bridges

Various aspects of a general finiteelement program for the nonlinear analysis of steelandconcrete structures is described. The program accounts for the nonlinear behavior of concrete, steel, and shear connectors. Concrete is treated as an orthotropic nonlinear material. The concept of equivalent strain is used to establish independent stressstrain relationships in the directions of orthotropy. Steel is modeled as an elastoplastic strainhardening material, and classical theory of plasticity together with the von Mises failure criterion is applied. For shear connectors, an empirical nonlinear shear forceslip relationship is used. The accuracy and reliability of the program are demonstrated by the analysis of two composite beams and a multigirder bridge over the entire loading range up to failure. The analytical results are compared with the corresponding experimental andor field data with good agreement between the two. The reported results demonstrate the feasibility and reliability of the nonlinear finiteelement method as an expedient alternative to costly experimental work in some situations.