Study On Seismic Performance Of High-strength Concrete Columns With Multiple Composite Central Reinforcement

Nowadays,with the rapid development of Metro in our country,at the same time,the commercial complex of Metro overhead property emerged one after another.The emergence of Metro overhead property business not only alleviates the problem of extremely scarce land resources,but also promotes the rapid development of the surrounding economy to a large extent,forming a new mode of redistribution along the Metro line,which promotes the old one.Urban renewal,new town construction and the transfer of residential space from urban to suburban areas have broad prospects for development,which has attracted extensive attention of Engineering designers.A large number of earthquake disasters show that the improvement of seismic performance of reinforced concrete columns are very important to solve the seismic performance of complex frame structures when developing such complex structures in high intensity areas.Based on the practical engineering of Donggang Vehicle Base of Lanzhou Metro Line 1,this paper combines stirrups with common reinforced concrete columns on the basis of cross-section reinforcement form to form multiple composite central columns,and then restrains the transverse deformation of internal core concrete,so as to improve the mechanical properties of concrete columns.In view of the seismic performance of high-strength concrete multiple composite columns,the following research work has been carried out in this paper:(1)The low-cycle repeated loading tests of eight high-strength concrete multiple composite central columns were completed.The effects of axial compression ratio,stirrup spacing,stirrup ratio and stirrup form on the seismic performance of the new type of central columns were investigated.The results show that the effect of axial compression ratio on the seismic performance of the central columns is the greatest,followed by stirrup spacing and stirrup ratio,and the stirrup form has the smallest impact on the central columns.(2)The performance differences between the central column with multiple composite central reinforcement and ordinary reinforced concrete columns are studied from the aspects of strength degradation,stiffness degradation,displacement ductility and energy dissipation.The results show that the multiple composite central columns have high bearing capacity and good ductility,and the seismic performance of this new type of central columns is significantly better than that of ordinary reinforced concrete columns.(3)By analyzing the stiffness degradation law of high-strength concrete multiple composite central columns under different parameters,the stiffness degradation formula of loading and unloading is obtained by regression fitting method,and the restoring force model of this new type of core columns is established by combining with the simplified three-fold skeleton curve model.(4)Referring to the calculation method of shear bearing capacity of ordinary reinforced concrete columns in current codes of our country,the confinement of composite stirrups in high-strength concrete multiple composite central columns to concrete in different regions is divided into core area,tube area and common area and calculated separately.The calculation formula of shear bearing capacity of this new type of central columns is obtained,and the theoretical value of the bearing capacity calculated by the formula is compared with the experimental value.The results show that the average value of the ratio of the experimental value to the theoretical value is 1.08,and the standard deviation is 0.03.The proposed formula can be used to calculate the shear capacity of high-strength concrete columns with multiple composite central reinforcement and the design suggestions of core columns are given.