Study On The Seismic Behavior Of Interior Joint Of Prefabricated Cage System In Prefabricated Concrete Frame

The steel cage concrete has the advantages of high bearing capacity and good ductility.At the same time,it is convenient for factory production and it is beneficial to the cost savings,construction period shortening.However,the steel cage concrete research is insufficient.The steel cage concrete interior joint was the weak area of the steel cage concrete framework and has great influence on seismic behavior of the whole structure.Thus it is necessary to systematically study the seismic performance of the steel cage concrete interior joint.The mechanical properties and working mechanism of the steel cage concrete joints are analyzed by means of numerical simulation in this paper.Combined with constrained concrete constitutive model and softened struct-and-tie model,the finite element models of steel cage concrete was proposed and the prediction result of seismic performance were obtained.The main research contents are as follows:1)Based on the similarity theory and the equivalent conversion,the quasi-static test of the joint specimens of a set of steel cage concrete frame is designed according to the existing Code for Building Seismic Design（GB50011-2010）.The specimens include the cast-in-situ steel cage concrete interior joint,the cast-in-situ reinforced concrete interior joint,the prefabricated steel cage concrete interior joint and the whole cast-in-situ steel cage concrete interior joint.2)Based on the large-scale universal finite element software ABAQUS,the finite element simulation of the seismic performance in the existing reinforced concrete joints was carried out by using the solid element model and the fiber-beam element model respectively.The results were compared with the numerical simulation results and the results of the comparison show that the numerical simulation results of the seismic performance of the joints obtained from the fiber-beam element model are in good agreement with the experimental results and the simulation results of the seismic performance of the joints based on the solid element model are closer to the experimental results.The results show the effectiveness of fiber-beam element model in seismic performance simulation of reinforced concrete,the selection of elements in the model and the rationality of material constitutive model.3)Based on the above-mentioned reinforced concrete fiber-beam element joint model,the beam and column adopt the beam element,and the core area of the joint adopts the softened struct-and-tie model.The steel cage fiber-beam element model is obtained by using the increase coefficient K_pcs according to the same core concrete restraint mechanism.The results of the existing steel cage concrete joints and the numerical simulation results which were calculated in ABAQUS were compared and the results of the comparison show the effectiveness of fiber-beam element model in seismic performance simulation of steel cage concrete,the selection of elements in the model and the rationality of material constitutive model.4)Based on the model of the reinforced concrete fiber-beam element joint model and the steel cage concrete fiber-beam element joint model,the nonlinear finite element analysis of the seismic performance of the joints in the steel cage concrete and the reinforced concrete in the experimental design of this group is carried out.And the seismic performance of the concrete in steel cage under different axial compression ratio is predicted and the results show that the overall seismic performance of the joints in steel cage concrete is better than that of reinforced concrete in the same strength.