Experimental Study On Seismic Performances Of Precast Concrete Frame Connections With Rebars Of Large Diameter And Enlarged Spacing

The application of high-strength rebars with large diameter and enlarged spacing can effectively ease the construction at joints, enhance the efficiency of assembly, and thus greatly promote the development of precast concrete structures. For the precast concrete structures using this type of reinforcement, their seismic performance is of concern and has attracted a lot of research attention lately.This paper reports an experimental study on the seismic performance of precast concrete frames using the high-strength and large diameter rebars. 4 full-scale precast concrete frame joints are tested. They are respectively 2 cross-shaped joints and 2 T-shaped joints. The beams and columns are all reinforced by the high-strength and large diameter rebars. The bottom longitudinal rebars in the beams of the cross-shaped joints as well as all the longitudinal rebars in the beam of the T-shaped joints are anchored to the anchor plates in the post-pouring joint region. The objectives of the tests are to investigate the structural behavior, failure mechanism, and seismic performance of the specimens under low cyclic loads. The main findings are as follows:1) The failure of each joint is resulted from the flexural failure in the plastic hinge region at the end of the beams, while the joint region generally remains in the elastic state. Therefore the joins possess relatively good ductility and energy dissipation capacity.2) The cross-shaped joins have an equivalent seismic performance compared to the T-shaped joints. Both types of the joints have good seismic performance.3) The anchorage used to connect the longitudinal rebars of the beams in the joint zone is safe and reliable, and its design by calculation can be carried out according to the relevant standard of China.4) Finally, the tests prove that the structural integrity of the joints under cyclic loading can be ensured by the detailing measures, such as roughness processing of concrete interface, indented concrete faces, grouting of sleeves and stirrup arrangement.The ABAQUS software is used to perform non-linear finite element analysis(FEA) for the joint specimens. In the FEA, the joints are simulated by the cast-in-situ integral model. It is found that the FEA results are in good agreement with the experimented results before the longitudinal rebars of the beams yield.