Study On Seismic Behavior Of Rocking Column Structure With External Connection Of Column End

As an important form of restorable functional structure,rocking column is significantly different from traditional structure.It can reduce the lateral stiffness of the structure through disconnection from the foundation or nodes,generate sway in the process of earthquake,reduce the acceleration response of the structure,and improve the seismic performance of the structure.In the traditional form of rocking column structure,in this paper,external connecting bars are set at the base of swing column to form a rocking column structure with external bars at the end of the column.The external reinforcement can not only facilitate the installation of the column in place,but also achieve the goal of shock absorption and energy consumption.The main contents of this paper are as follows:(1)Based on the existing experimental study of rocking column(Roh2010),the finite element model is established by using ABAQUS platform.By comparing with the test results,the rationality of the finite element model is verified.On this basis,the parameter analysis of rocking column is carried out,and the influence law of concrete strength,axial compression ratio and other factors on the mechanical properties of rocking column is studied.The results show that the axial compression ratio affects the mechanical properties of rocking column The main factor is that the concrete strength has little effect on the bearing capacity and self restoring capacity of the rocking column.(2)Based on the traditional rocking mechanism of rocking column,a new type of rocking column is proposed,and the corresponding finite element model is established.The results show that the parameters of the external reinforcement are the main factors that affect the mechanical properties of the rocking column with a single FRP external reinforcement and a composite FRP external reinforcement.The FRP reinforcement can enhance the bearing capacity of the column in the case of large lateral displacement,which can improve the bearing capacity of the column in the rocking stage.The ideal flag type lag can be obtained by using the FRP external reinforcement rocking column The seismic performance of sway column structure can be optimized by adjusting the proportion of FRP bars and steel bars.(3)Based on the analysis of the parameters of the finite element model of the rocking column connected with the external reinforcement at the end of the column,the influences of the mechanical parameters such as the concrete strength,the axial compression ratio and the external reinforcement on the mechanical properties of the rocking column are examined,and the influences of the ratio of the reinforcement and the FRP reinforcement on the seismicperformance of the column are studied.The results show that the axial compression ratio and the external reinforcement type are the key factors affecting the seismic performance of the new rocking column.And compared with the performance of the test rocking column,the seismic performance evaluation indexes of the column are proposed from the hysteresis curve,residual deformation,equivalent viscous damping coefficient,equivalent stiffness,initial stiffness,peak bearing capacity and other aspects.(4)Based on the simulation results,the calculation methods of the moment curvature relationship of the cracking critical point,the yield critical point and the rocking critical point are obtained,and the rationality of the model is verified by comparison.Based on the theoretical model,the finite element model of beam element + connection element is established,which is compared with the results of fine finite element model and multi-scale finite element model to verify its rationality and lay a foundation for the later analysis of rocking column structure.(5)Based on the beam element + connection element,a three-story three span frame finite element model is established,and the elastic-plastic time history analysis is carried out to simulate its mechanical behavior under rare earthquake.By comparing with the traditional frame,the effect of improving the seismic performance of the whole frame structure by the rocking column connected with the external reinforcement at the end of the column is evaluated.It is found that the frame structure with rocking columns can reduce the story shear response of the structure.By adjusting the configuration of external reinforcement,the lateral stiffness of rocking columns can be designed,so as to avoid the weak story of the frame in the process of earthquake.