Study On The Hysteretic Performance Of Self-Centering Post-Tensioned Precast Concrete Frame Structure

China's construction industry must take the road of adjustment and transformation to meet the needs of modern urban construction.At this stage,the state and the government are vigorously promoting the industrialization of buildings and the development of green buildings.On the other hand,existing cast-in-place RC frame structures and prefabricated RC frame structures in our country have almost no deformation recovery capability,which leads to serious damage and cannot be reset independently after earthquake.Therefore,the repair cost is high,and it is difficult to meet the requirements of modern urban construction and development.This article will propose a self-centering prefabricated RC frame joints,which has the characteristics of self-centering,assembly,low damage and easy repair,which not only meet the seismic requirements,but also accord with the concept of building industrialization and green building development.In this paper,a self-centering prefabricated RC frame joint is proposed,and the joint design and experimental research are carried out.The main research is the seismic performance of hysteretic performance,self-centering function,energy dissipation capacity and damage degree.The experimental results show that this joint has obvious self-centering function under low cyclic reciprocating load,and only a few cracks appear toward the beam end.Compared with the failure degree of cast-in-situ structure,this joint has low damage characteristics obviously,and can be easily repaired,fully reflects its advantage after the earthquake advantage.The restoring force model of the self-centering prefabricated RC frame joint is proposed,which is divided into three stages: the effective linear limit state,the yield state of the energy-consuming reinforced bar and the limit state.By theoretical analysis of deformation coordination and equilibrium equations,the theoretical analysis of the moment-rotation relationship of the self-centering prefabricated RC frame joint under each condition is carried out.The theoretical calculation results has good agreement with the test results.The theoretical calculation formula deduced in this paper can accurately predict the moment-rotation relationship of the self-centering prefabricated RC frame joint at each stage and provide a theoretical basis for the study of the mechanical properties of the self-centering prefabricated RC frame joint.Based on the finite element analysis software of OpenSees,a numerical simulation method of the self-centering prefabricated RC frame joint is proposed.The nonlinear fiber beam-column element based on the flexibility method is used to improve the computational efficiency of the model.The constitutive model solves the mechanical behavior simulation problem at the contact surface of beam and column.By using Steel02 unit,the initial redressing simulation of redressing tendons is solved by setting the unit parameters.The numerical simulation results are good agreement with the experimental results in the load-displacement curve and P-? curve of tendons of the self-centering prefabricated RC frame joint.It shows that the numerical simulation method proposed in this paper can accurate simulate the stress situation and the change of the redressing force under the cyclic low-cyclic loading of the self-centering prefabricated RC frame joint,which will lay a solid foundation for the later non-linear analysis of the prefabricated RC frame.The design and numerical simulation of a RC frame are carried out based on the design and numerical simulation of the self-centering prefabricated RC frame joint.The results show that self-centering prefabricated RC frame has good hysteretic performance,good energy dissipation capability,and obvious self-centering function,which achieves the expected design results.In order to study the effect of the self-centering prefabricated RC frame joint on the overall seismic performance of RC frame structures,the engineering examples and self-centering prefabricated RC frame structures are modeled in 3D based on OpenSees and SAP2000 finite element analysis software,to static non-linear pushover analysis and seismic performance evaluation.The results show that the self-repositioning prefabricated RC frame structure and engineering examples can achieve the expected seismic performance level under the action of rare earthquakes.The difference is that the overall stiffness of the self-centering prefabricated RC frame structure is smaller than that of the engineering example,and the number of nonlinear hinges reaching the effective linear limit state is more than that of the engineering example when the building structure reaches the performance point.This indicates that the plasticity of the beam can be opened and closed at the joint of beam and column joints of the self-centering prefabricated RC frame structure to reduce structural damage.On the other hand,the ultimate bearing capacity of the self-centering prefabricated RC frame structures is comparable to or even superior to that of cast-in-place RC frame structures.Therefore,it is of great significance to do some scientific research on this kind of concrete frame system with the characteristics of the self-centering and low damage and apply it to the actual project.