Research On A New Type Beam-to-Column Joint Of Precast Composite Frame Structures

With the acceleration of urbanization in China,the development of construction industry in China is undergoing structural adjustment,transformation and upgrading in an all-round way,and it promotes the new construction industrialization focusing on the development of the precast buildings actively.However,as far as the current popularization of assembled structures in China is concerned,most of the existing beam-column joints have complex structures and need large amount of temporary steel pipe support in site,which seriously hinders their largescale popularization and application.Therefore,in order to speed up the process of construction industrialization in China,it is urgent to develop new connection joints which are simple,efficient and feasible to construct.Supported by the 13 th Five-Year National Key Research and Development Program of China(2016YFC0701703),this paper summarizes the shortcomings of existing beam-tocolumn joints of precast concrete frame structure,and proposes a new type of beam-to-column joints of precast composite frame structures creatively,considering factors such as production,construction and mechanical properties.This new type of joints refers to the connection form of beam-column joints of steel frame,inherits the advantages of safe,reliable,simple and efficient installation technology of steel frame,combines the economy of pre-tensioned concrete beams,and realizes ductility design by referring to the method of controlling the plastic hinge position in beam-column joints of steel frame,which has a good application prospect.In this paper,the seismic performance of this new type of joint is preliminarily explored by carrying out low-cycle repeated load test and numerical simulation analysis.The main work and achievements of the paper are as follows:(1)This paper introduces the construction and the fabrication method of components in this new type of beam-to-column joints of precast composite frame structures,explains the design idea of joints from type selection and plastic hinge control,and analyses the advantages of joints in the new type precast composite frame structures.For the multi-storey precast composite frame structure with this new type of beam-column joints,this paper presents the standard construction and installation process in order to guide the actual project.(2)Six full-scale joint specimens are designed and manufactured to carry out low-cycle cyclic loading tests(three exterior joint specimens and three interior joint specimens).They are divided into three types: ordinary joints,weakened joints with dog bones on beam flange and weakened joints with opening on beam web.Based on the experimental phenomena and data analysis,the failure modes,hysteretic curves,skeleton curves,yield strength,ductility,stiffness degradation and energy dissipation capacity of the specimens are obtained.The research shows that the beam-column joints of the new precast composite frame structure can control the displacement of the plastic hinge according to the method of steel frame joints.By weakening the flange of the beam,the position of plastic hinges can be accurately controlled.The ductile steel can be used to dissipate energy.The hysteretic curve of the joints is full shuttle-shaped,the bearing capacity is stable and the energy dissipation capacity is strong.It effectively improves the seismic performance of frame structure and achieves the purpose of ductility design.However,the plastic hinge can not be controlled in the steel end connector by opening the web of the beam.The mechanical performance of the joint is not significantly different from that of the common joint,and the ductility and energy dissipation capacity are poor.(3)The finite element analysis platform OpenSees was used to model the specimen under low-cycle repeated loading,and the rationality of the modeling method was verified by comparison with the experimental results.On this basis,the parametric analysis of the new beam-column joints is carried out,which provides a basis for further optimization of the node structure.Through the above research work,this paper makes a comprehensive analysis of the component fabrication,construction method and seismic performance of the new type of beamto-column joints of precast composite frame structures,which provides some experimental data and theoretical basis for the further improvement and popularization of the new type of joints.