Performance Design Of Joint In Assembled Monolithic Concrete Frame Structure

With the gradual advancement of the new urbanization in China,the modernization of the construction industry has gradually become a hot direction.The Scope is a post tensioned precast prestressed concrete frame structure system which is imported from France.With the high production efficiency,good construction quality,sustainable development,the scope system fits the requirements of the construction industry in new development situation.In order to elaborate the advantage of precast concrete structure,based on related documents at home and abroad,the performance of beam-column joints is optimized.In this paper,six full scale prefabricated prestressed concrete frame joints are designed,and their seismic performance is studied by low cyclic reversed loading test.Then the finite element numerical analysis of the test node is carried out,and the testing results are compared with the simulation results.Finally,the calculation method of the ductility of beam column joints is put forward,and the Function-Oriented design of the seismic behavior of beam column joints and members is proposed based on the damage model.In detail,this study includes topics as follows:(1)The design parameters of the six full scale beam-column joints are the concrete ductility in the core area and the reinforcement ratio of the beam longitudinal reinforcement.Through low cycle reversed loading,the hysteretic curves,ductility,energy dissipation capacity and stiffness degradation of six nodes are analyzed,and their seismic performance is quantitatively evaluated.(2)The OpenSees is used to simulate the low cycle reversed loading tests of the nodes,and the results are compared with the experimental results.The simulation results show that the beam column fiber model and beamcolumnjoint macro joint model based on OpenSees platform can well simulate the process of joints under low cyclic loading.The hysteresis curves agree well in the test and simulation results.And the unloading of the specimens under various cycles,as well as the stiffness degradation,strength degradation and pinching effect of the specimens are accurately predicted.(3)The deformation composition of the beam-column joints is deconstructed and the Function-Oriented calculation method for joint ductility is proposed.Based on this,the Function-Oriented seismic design method based on the concrete damage model is put forward,and the coupling relationship between beam-column joints deformation ductility,energy dissipation capacity and damage is discussed.Finally,a three parameter damage model considering the stiffness degradation is proposed,which can be used to further predict the seismic performance of beam-column joints.The ultimate failure state of the six nodes in this paper is the plastic hinge at the end of the beam.The core area of the high reinforcement ratio test parts produces oblique cracks but the shear deformation is small,and it is still in the category of elastic deformation,which satisfies the regulations of China’s seismic code well.The core and keyway area modified with fiber reinforced concrete can increase the deformation capacity of beam-column joints.The nonlinear finite element software OpenSees can be used to simulate the mechanical behavior of beam-column joints under low cyclic loading.The Function-Oriented design method of the performance of beam-column joints is in good agreement with the experimental results,and has a certain research prospect.