Seismic Experimental And Theoretical Study On A New Precast Concrete Connection Which Strand Anchored Into Core Area

Into the "the Twelfth Five-year" plan, along with accelerating the urbanization process of our country, the state vigorously promote the construction of industrialization, in order to achieve the transformation and upgrading of the construction industry, construction of energy-saving, Conservation of land and environment-residential increasingly become the target and direction of China’s housing construction.Precast concrete with high production efficiency, product quality, small impact on the environment and conducive to sustainable development and so on. In the precast concrete structure, precast concrete frame and shear wall structure is the main form of two types of structure, the application surface of frame structure is wide. In recent years, many domestic scholars have done a lot of research on seismic behavior of precast concrete frame structures, this paper is based on the existing research results, we propose a new type of precast concrete frame connections and carried out the seismic performance experimental and theoretical studies, the main work and achievements are as follows:1 Analyzes the important significance of developing precast construction technology to construction industry of our country, review and summarize the relevant technologies and research results of precast concrete frame structure, existing problems of our precast concrete structure.2 Based on the basis of existing studies, innovative proposed a new precast frame connection which the strand anchored into the joint. Starting from the principle of energy dissipation mechanism, analyzes its energy dissipation mechanism by theoretical way, and evaluation of the energy dissipation capacity of the new connection. In order to grasp the seismic performance of the new connection, designed and produced four new connections and a cast-in-place connection, where different points of the four new precast connections whether the connection setting additional reinforcement and strand within the keyway is set free bond segment. A detailed description of the specimen design, loading equipment and loading system and the required measuring content of the test process.3 Take low reversed cyclic loading tests to 4 new precast concrete frame connections and a cast-in-place connection, and compared hysteresis curves and skeleton curves, deformation capacity and capacity analysis, stiffness degradation, energy dissipation capacity, inter-layer displacement angle and steel strain. Experimental results show that the new connection when the beam end bear the upward load, that strand as the main force tendon, its hysteresis curve showing the bow, the full extent inferior cast-in-place connection. Skeleton curve of the new nodes upward have no obvious yield platform segment, its ultimate bearing capacity with respect to the cast-in-place specimen improve more. Precast connection stiffness degradation, hysteretic energy, equivalent viscous damping coefficient is not as good as cast-in-place specimen in the early. But in the late loading stage, These indicators are greatly improved with respect to cast-in-place specimen, it illustrate that precast node has a large safety margin. The new node displacement ductility factor lower than cast nodes, but the deformation capacity of precast connections roughly equal to the cast-in-place specimen.4 Introduced several models of restoring force of reinforced concrete structure or specimens, and for which a type restoring force model (Tri stiffness degradation restoring force curve model) for the corresponding mathematical description. Based on the hysteretic and skeleton curves of new precast connections which obtained by the test, through the skeleton curve dimensionless processing, establish a unified skeleton curve to all the new precast connections, and compared dimensionless skeleton curves which obtained by the test, It can be found in well conform with the experimental results. Finally, obtained mathematical model of stiffness degradation laws for 4 new precast connections under low cyclic loading by regression analysis.6 On the basis of the existing "Seismic Design of Buildings" and the transfer mechanism of core area in-depth study, calculated checking effective width, height and effective depth of all specimens in this paper. Analyzing the beam bending failure, end-column bending damage, anchor damage and the shear failure in core area of connections, designed to avoid the other three forms brittle fracture in addition to bending failure of the end beam. The main destroyed reason is that the insufficient concrete constraints, insufficient reinforcement, anchorage reinforcement problems of beams and construction improper. Therefore, measures taken for the design of the from the strength and ductility construct, it can improve the seismic performance of connections. Using improved compression field theory (MCFT) to calculate the shear strength and shear deformation of new precast connections. The results show that using MCFT mechanism can better predict the shear strength and shear deformation of new precast connections, the load-carrying situation of new precast connections are complex.7 on the basis of concrete damage plasticity constitutive model and repeated estimates, determine the parameters of the new node for finite element analysis, through finite element software ABAQUS to establish model and analysis for new nodes, compared the numerical simulation results with experimental results,it can be found that the hysteresis curves, skeleton curves by simulating have a good degree of agreement with the hysteresis curves, skeleton curves by experiment. Verify that established the finite element model in this paper to simulate the seismic performance is feasible.8 It summarizes the main results of this paper points out the key issues precast concrete frame structure needs to be further studied.