Study On Seismic Behavior Of T-Shaped Shear Wall With HRB600 High Strength Steel Bars

Promoting the engineering application of high-strength steel bars is an important demand for the development of the current construction industry.Although HRB600 grade rebars has been listed in the newly revised steel product catalogue,the corresponding basic experimental research is less,and the existing structural design code does not include 600 MPa grade rebars,which leads to certain obstacles in its application.Therefore,Therefore,the quasi-static test of shear wall with HRB600 high-strength grade rebars is carried out,and its seismic performance is comprehensively evaluated by numerical simulation and theoretical analysis to provide a theoretical basis for the popularization and application of 600 MPa garde rebars.The main research contents and conclusions are as follows.Three T-shaped shear walls and one I-shaped shear wall with HRB600 high-strength rebars were designed and manufactured.The bearing capacity,failure mode,stiffness degradation,deformation and energy dissipation of the walls were analyzed by low-cycle reciprocating loading.The effects of axial compression ratio,loading direction and section form on the seismic performance of high-strength reinforced shear walls were compared and studied.The test results show that ductile bending failure occurs in all specimens,and the ultimate displacement angle of the specimens is greater than 1.83%,which shows that the shear wall with 600 MPa grade rebars still haver good deformation capacity.The compressive strength of 600 MPa grade rebars at the compressive edge of the wall can reach the same value as the tensile strength,and the strength of high strength steel bars can be fully exerted.The damage of T-shaped shear wall occurs in the boundary element of the free end of web.The bearing capacity of the flange in tension direction is higher,the initial stiffness is larger,but the deformation capacity and ductility of the flange in compression direction are stronger.The larger the axial compression ratio is,the higher the bearing capacity of the shear wall is,the worse the corresponding deformation capacity is.When loading along 45 degrees,the bearing capacity of the T-shaped shear wall will be reduced,but the ductility in this direction is better than loading along the web direction.Compared with the I-shaped shear wall,the positive and negative bearing capacity of T-shaped shear wall can be improved by the existence of flange,but the corresponding bearing capacity and stiffness degenerate rapidly.A numerical model of T-shaped shear wall considering bending-shear coupling is established by using OpenSees analysis program.The accuracy and rationality of the model are verified by comparing the simulation results with the experimental ones.On this basis,the effects of axial compression ratio,concrete strength,reinforcement strength,length of edge constraint zone and longitudinal reinforcement ratio on seismic performance of T-shaped shear wall with high strength reinforcement are studied by using the verified finite element model.The results show that the ductility of shear walls under high axial compression ratio is poor and brittle failure may occur.Increasing the strength of concrete and the ratio of longitudinal reinforcement in edge restraint zone can improve the bearing capacity,deformation and energy dissipation capacity of walls to a certain extent.When the principle of equal strength replacement is adopted,the strength of rebars has little effect on the bearing capacity,but when high strength reinforcement is used,the ductility of shear walls will be improved.The seismic performance of T-shaped shear wall can be improved by increasing the length of the edge restraint zone,while the restraint component at the intersection of web and flange has little effect on the seismic performance of T-shaped shear wall.This paper also calculates the load-displacement of T-shaped shear wall,studies the applicability of current codes to T-shaped shear wall with HRB600 rebars,and gives the strength design suggestions of 600 MPa grade rebars for calculating the bending capacity.On the basis of experiments and reasonable calculation assumptions,a four-fold-line skeleton curve model of T-shaped shear wall is established.The model can consider the effects of bending deformation,shear deformation and steel slip on wall deformation.At the same time,the formulas for calculating load and displacement of shear wall in cracking,yield,peak and ultimate states are derived.To verify the rationality of the model,the calculated data are compared with the experimental data.The results show that the calculated skeleton curve of T-shaped shear wall is in good agreement with the experimental results.The errors of load and displacement are within 7.5% and 12.01% respectively.The free end of web is the weak part of T-shaped shear wall,so,in the end of this paper,some suggestions for the design of edge restraint members of T-shaped shear wall are put forward.