Seismic Performance Of Rocking Buckling-Restrained Braced Reinforced Concrete Frame

Buckling-restrained brace frame(BRBF)structure is an efficient lateral structural system.But the axial force generated by slant BRB in the high-rise BRBF structure accumulates on the bottom column,which is easy to cause the failure of the bottom column.Rocking structure system is a new type of structure system that relaxes the constraints between superstructure and foundation or between components,so that the contact surface is only under pressure but not under tension to ensure that the structure can be lifted under earthquake action,and the rocking behavior is formed through the restoration mechanism.Combined with the characteristics of the BRBF and the rocking structure,the rocking column feet are installed on the bottom column of BRBF to form the rocking buckling-restrained braced frame(RBRBF)structure system,which releases the axial force of the bottom column and effectively reduces the structural damage,and is convenient for post-earthquake repair.This research group has carried out experimental studies and numerical simulation on rocking buckling-restrained brace steel frame,and experimental studies on rocking buckling-restrained brace reinforced concrete frame.In this paper,numerical simulation studies on rocking buckling-restrained brace reinforced concrete frame are carried out based on Open Sees.According to the pseudo-static tests of BRBF and RBRBF completed by the research group,the two-dimensional finite element numerical model of the test framework was established.The simulation results were in good agreement with the experimental results,which indicated the correctness and rationality of the modeling method of two-dimensional finite element model,and provided a basis for the modeling method of three-dimensional finite element model and further research of BRBF and RBRBF.Due to the experimental conditions and financial constraints,the research group only carried out the experimental research on the three-storey substructure model of BRBF and RBRBF,so that the numerical model of the whole structure was established.Considering that three-dimensional model can make up the deficiency in two-dimensional model,and more truly reflect the structural responses,comparative analysis the elastic-plastic time-history analysis results of the three-dimensional and two-dimensional finite element model of BRBF and RBRBF,the results show that the three-dimensional finite element model has good reliability.When BRB and rocking column foot arranged in two directions,the bidirectional stiffness of RBRBF is distributed uniformly,and the structural response of RBRBF has been reduced.Considering that there are structures with different storey number in actual engineering,and the storey number will also affect the structure response of RBRBF,structures with 4,8and 12 floors were established to perform the parametric analysis.Firstly,the influence of the lateral stiffness ratio between the BRB and the main frame and the arrangement of the BRB on the seismic performance of BRBF with different storey numbers were studied.Secondly,the model of RBRBF was established based on the optimized model of BRBF.Finally,the parameters of three-dimensional model of rocking column foot,including the section area and yield strength of the damper,were selected,and the elasto-plastic time-history analysis of RBRBF was carried out with different storey numbers,combinations of BRB lateral stiffness ratio and arrangement,and the parameters of the rocking column foot.The results show that the BRB can be arranged centrally when the lateral stiffness is small,but should be arranged evenly in each span in both directions when the lateral stiffness is large.RBRBF converts ground motion energy into structural rigid body motion,which reduces the deformation of BRB and the main structure.The deformation of RBRBF is mostly caused by the rigid body motion,but the deformation caused by the load is far less than that of BRBF.RBRBF adjusts the structural characteristics through the rocking behavior,making the structure stiffen to provide the required lateral stiffness and become flexible to avoid serious seismic response,and maintaining a higher lateral stiffness when stop rocking.The reduction ability of RBRBF on the maximum bottom column tension is higher when BRB arranged evenly in each span in both directions,and the reduction degree is higher with the increase of the lateral stiffness ratio and the storey numbers,and with the decrease of the section area of the damper of the rocking column foot.The effect of rocking column foot in high-rise BRBF is better than that in low-rise BRBF,and the sensitivity of high-rise RBRBF to the stiffness and strength of the damper of the rocking column foot is higher than that of low-rise RBRBF.