BEHAVIOR OF PRECAST CROSS BEAM – MAIN GIRDER CONNECTIONS IN BRIDGES

Abstract

In the last few decades, precast concrete has become strongly recommended for the most types of bridges construction due to time saving, quality control and concrete members’ consistency. In bridges construction, precast concrete elements are connected (Stitched) together in order to achieve bridge deck integrity and stability; joints between these elements shall be able to transmit all internal forces due to anticipated loads safely. This research introduces an experimental and analytical study of the performance of stitching joint between precast beams, and determines if this detail could generate a precast deck system that could emulate the monolithic cast-in-place deck systems without any disadvantages to stitching concrete joint over monolithic one regarding material properties. In this respect, an experimental program was conducted on seven specimens, which were tested to failure under a static vertical load. Three specimens of monolithic cast-in-place beam-to-beam connection and four specimens of precast beams with stitching joints were tested using different positions of vertical load to simulate flexural tension or diagonal tension shear failures. Nonlinear 3D finite element analysis was performed using ANSYS program and verified with the experimental results in order to give design recommendations for adoption of this type of precast joints. In addition, a parametric study as well as verification with international design codes was made to conclude the effect of stitching joint length on joint capacity and performance of cross beams. Results obtained by both experimental and analytical works indicated that stitching joints have a reduced flexural capacity compared to monolithic joints, while two types of joints have the same shear capacity after checking shear friction failure of stitching joint. Parametric study has proved that increasing stitching length enhances capacity and performance of joint between precast main girder and cross beam in flexure.