Experimental and numerical investigations on force transfer mechanism of steel-concrete joint in hybrid girder bridges

Steel-concrete joint is the core force transfer node of hybrid girder bridges. However, the load transfer mechanism of steel–concrete joint has not been understood enough, due to the material discontinuity, abrupt change of stiffness, and complex structure. In this paper, the model test of a typical steel–concrete joint in hybrid girder bridges and the push-out tests of its main force transfer components were carried out. The load-slip curve, stress distribution, and failure mode of the specimens were compared and discussed. The test results show that the steel–concrete joint possesses favorable axial stiffness and bearing capacity. The ultimate failure mode of the joint was reached when the steel beam segment adjacent to the steel–concrete joint buckled. However, the steel–concrete joint was still comparatively intact and in the elastic state during the loading process. In addition, the internal force transfer mechanism and characteristics of the steel–concrete joint were analyzed by finite element method. In terms of the force transfer rate, the bearing plate, perfobond leiste (PBL) connectors, and end face of the T-shaped steel girder transferred 72.9 %, 7.9 %, and 19.2 % of the total axial force, respectively. The redundancy analysis shows that the bearing capacity redundancy of the joint is 1.52. The joint has sufficient bearing capacity redundancy, but the ultimate bearing capacity of the joint as well as its adjacent areas is determined by the axially loaded steel beam segment.