Research On Seismic Performance Of PVA-ECC Reinforced Frame Beam-column Joints

ECC(Engineered Cementitious Composites)is a highly ductile fiber-reinforced cement based composite material with pseudo-strain hardening characteristics and multi-crack development mechanism.As a toughening material,fibers can improve the tensile strength,shear strength,toughness,impact resistance,crack resistance,impermeability,abrasion resistance and durability of concrete.Compared with other high-performance concrete,ECC has more application advantages,which has attracted widespread attention in the scientific research and engineering fields.At present,there are few domestic and foreign cases about beam-column joints of ECC reinforced frame structure,which deserves further study.Based on domestic and foreign research,this paper uses PVA fibers produced in Japan to conduct in-depth and detailed research on the seismic performance of beam-column joints of PVA-ECC reinforced frame structures.The specific work is as follows: 1.Based on the beam-column joint optimization design proposed by the team of Professor Pan Jinlong of Southeast University,a pseudo-static load test was performed on one ordinary concrete edge node,one PVA-ECC edge node,and one unconnected reinforced ordinary concrete edge node..The test found that no obvious damage occurred in the core area of the joints of the test piece,and no connection failure was found in the optimization of the longitudinal reinforcement of the beam and the connecting reinforcement of the test piece,so it was feasible to optimize the design of the connection.PVA-ECC structure has better seismic performance than ordinary concrete structure.During the loading process,the bridging action of PVA fiber improves the integrity of the test piece.PVA-ECC has better adhesion and ability to deform cooperatively than ordinary concrete and steel bars.The U-shaped connecting bars increase the yield displacement of the specimen.PVA-ECC can increase the displacement coefficient of structural members and enhance the deformation capacity;2.Based on ABAQUS finite element simulation software,a finite element model of beam column joints of PVA-ECC reinforced frame structure is established,and its mechanical performance under low-period reciprocating load is numerically simulated.Compare and analyze the numerical simulation results and experimental results in two aspects.The agreement between the two is very high,and the established finite element model is more accurate and reliable,which can better simulate the mechanical performance of PVA-ECC material frame structure;3.Based on the model verification,a finite element model of PVA-ECC reinforced frame structure was established,and the differences of hysteresis curve,steel bar strain and concrete stress cloud diagram of frame structure under different PVA-ECC pouring lengths and material strengths were analyzed.The pouring length and material strength of PVA-ECC have a certain effect on the seismic performance of the structure.Due to the low elastic modulus of PVA-ECC,increasing the pouring length will reduce the bearing capacity of the structure,but PVA-ECC can improve the deformation capacity of the structure That is,ductility can also enhance the energy dissipation capacity of the structure and thus improve the overall seismic performance;increasing the strength of the PVA-ECC material can enhance the bearing capacity of the structure;the greater the strength of the PVA-ECC material,the ultimate displacement and ductility coefficient also increase,indicating that increasing PVA-ECC strength can effectively improve the seismic performance of the structure,and is beneficial to improve the deformation of the structural unit.