Research On SRC Beam-column Joints Element Model Based On OpenSEES

The steel reinforced concrete structures are widely used in high-rise and industrial buildings due to their high bearing capacity,high rigidity and good ductility.As the frame structure,the beam-column joints transmit the internal force and connect the key parts of the beam and column.They are in the state of compression and shearing composite stress,and their safety and reliability are the premise to ensure the normal operation of the structure.The earthquake disasters at home and abroad show that the frame joints are prone to different degrees of damage during the earthquake,and the damage forms are various.Therefore,the force characteristics of the joint zone must be considered when performing numerical simulation analysis of the frame structure.Because the force of the joint is more complicated,and the current beam-column joints element model is mainly developed for the reinforced concrete joints,it is not convenient to directly apply to the steel reinforced concrete beam-column joints,therefore,it is necessary to establish an element model considering the structural and mechanical characteristics of steel reinforced concrete joints.Based on the beam-column joints element model in Open SEES,this paper establishes a joint element model for numerical simulation of steel reinforced concrete structures and conducts a series of research work.The main research contents and conclusions are as follows:(1)Based on the existing beam-column joints element model of Open SEES,combined with the response characteristics of steel reinforced concrete beam-column joints under low-cycle repeated loading,a joint model of steel reinforced concrete beam column joints was developed.The element model carried out the position of the steel reinforced concrete slip spring.The correction adds a parameter that can consider the influence of the height of the upper and lower columns on the mechanical properties of the joint,and theoretically deduces the constitutive of the slip spring.(2)Combined with the force characteristics of the abnormal joints under low cycle repeated loading and the theory of the barred bar,the calculation program of the shear stress-shear strain relationship in the core region of the joint is written in Fortran language.Based on the open source code of the Open SEES,the new joint element model and the steel reinforced concrete slip spring constitutive model were implanted into it through secondary development.The correctness and applicability of the element model are verified by the numerical simulation of the low cycle repeated loading test of four abnormal edge nodes.The effects of axial load ratio,column longitudinal reinforcement ratio and steel distribution ratio on the seismic behavior of steel reinforced concrete beam column joints are studied by the ultimate bearing capacity,energy consumption and stiffness variation.(3)In order to further verify the applicability of the new joint element model in structural analysis,the four-section steel reinforced concrete frame is selected as the research object,and the new element model is applied to the quasi-static numerical simulation of the SRC frame.Rationality and applicability of the joint element model.