Precast(PC) concrete girder can be used economically for spans of up to 30m. Mostly, precast concrete girders are simply supported and continuous slabs are cast on these elements.
In this paper, the finite element program is presented for the analysis of the stress concentrations of the multi-span simply supported girders with continuous slabs. The study of the nonlinear behavior of composite bridges is quite complex. The difficulties can be attributed to the use of various materials and structural components, and to their behavior under different load conditions. The finite element method is a powerful tool which can be adopted to improve the understanding of the structural behavior of these bridges. The program includes the material nonlinearity of the concrete and steel reinforcements of the RC slabs, but assumes that the PC beam and cross beam behave linearly. In modeling the RC slabs and girders the four node degenerated shell element formulated based on the assumed strain interpolation and the 3D beam element are used, respectively.
The accuracy and reliability of the program are demonstrated by the analysis of a two span composite beam. Using the program, the influence of the magnitude of load, the existence of the cross beam, and the filling of open joints on the continuous slabs at supports are examined. In addition, for the purpose of examining the occurrence of initial cracks in the slabs at supports, the change of the compressive strength and the Young's modulus of concrete is considered as time-varying function.
As a result of this study, it is appeared that the best solution for the improvement of durability, appearance, and ride comfort of the PC bridges is to transform the individual spans into a fully continuous system by using thick diaphragms and a continuous deck slab at the supports. For the purpose of this solution, the proper method of constructing the perfect continuation of precast girder elements is needed.
