Seismic Performance Of New Precast Concrete Short Pier Wall Joint

The longitudinal reinforcing bar of the vertical bearing members of the precast building connected in the core area of the beam-column joints,which is also the junction of beam and column.Assembly surface is concentrated in the core area of beam-column connection,which limits the application of precast structures in high-rise buildings in seismic area.In order to apply precast structure in earthquake-resistant areas and meet the anchorage requirements specified in the code,a new type of beam-column connections were designed.Based on the experimental study of cast-in-place short-limb shear wall joints,a finite element analysis model of cast-in-place and precast structures was established by ANSYS software.According to the mechanical characteristics of interface of the precast structure,the shear friction constitutive relation were defined.The seismic performance of the short-pier shear wall joints using the new connection method is evaluated by the measured values of the existing test and the results of the two kinds of finite element analysis,such as bearing capacity,ductility,energy dissipation and stiffness degradation.The main findings are as follows:1.The proposed precast can meet the design requirements of anchorage connection of reinforcing bars stipulated in the current codes,and its finite element model proposed by simplified analysis is reasonable and feasible.The ductility and stiffness of the structure can be improved,when the axial compression ratio increases in a lower level.The strength of post-poured concrete should not be lower or larger than that of precast concrete.The diameter of longitudinal reinforcement distributed in the post-poured zone should not be higher than that of precast one,the distributed longitudinal reinforcement of precast shear wall and cast-in-place wall should be connected with equal strength.2.The parameters were analyzed by tests and finite element analysis method,such as the limb thickness ratio,axial compression ratio,shear span ratio,concrete strength,longitudinal reinforcement ratio of shear wall and beam,stirrups ratio of shear wall and beam.Then,the regression analysis of the descending stiffness and ductility coefficients was carried out to determined the restoring force model and established relevant formulas.After determining the main influencing factors of ductility,regression analysis is made on ductility coefficient,characteristic yield point,elastic stiffness,elastic-plastic stiffness and descending section stiffness and unified skeleton curve and hysteretic model considering unloading stiffness and reloading stiffness are established.It is found that the results are in good agreement with the calculated results and the restoring force model can be used as a reference for elastic-plastic seismic response analysis of precast short-limb structures.3.On the basis of the experimental study,the mechanical mechanism of precast short-leg shear wall joints is analyzed,which present that diagonal struts and truss working together in the structure.The model the formulas for calculating the shear capacity of precast short-leg shear wall joints based on modified compression field theory(MCFT)are established,which are combined with the enhancement of the effective width of the flange to the core area of the joints and the participation of the longitudinal reinforcement in the vertical force transfer mechanism.It turn out that the formulas are in good agreement with the test results...