Study On The Seismic Performance Of Precast Reinforced Concrete Hollow Columns

A new type of precast concrete hollow column is proposed in this thesis for the purpose of realizing the assembly of the structural components and pipelines at the same time,thus enhancing the construction efficiency of the precast concrete building.To investigate the seismic performance of the proposed hollow column and the reinforced concrete(RC)frame structure with hollow columns,four parts of studies are conducted,including the full-scale pseudo-static tests,the study on the finite element analysis method,the discussion about critical issues on the seismic design of hollow columns,and the assessment of the seismic performance of RC frame structure with hollow columns.The main outcomes of this thesis are as follows:(1)Based on the prototype structure,1 full-scale solid column specimen and 3 full-scale hollow column specimens are designed and tested under pseudo-static load.The failure mode,load-bearing capacity,deformation capacity and energy dissipation capacity of the specimens are analyzed.The influence of the hollow ratio and axial load on the seismic performance of hollow column are investigated.The results indicate that the spiral hoops produce effective confinement of concrete.Therefore,under the same axial loads,the ductility of hollow column is better than that of the solid column and their strength capacity are approximately identical.Hollow ratio has significant effect on the failure mode and seismic performance of hollow columns.In comparison with the solid column,the hollow columns with lower hollow ratio exhibits better ductility and a flexural failure mode is also observed.In contrast,the hollow column with a higher hollow ratio exhibits worse ductility and a flexure-shear failure mode is observed.The axial load also has a certain extent of influence on the failure mode and seismic performance of hollow columns.The hollow column with a lower axial load shows better ductility.(2)Based on the multi-layered shell model,a refined finite element analysis method of hollow columns is proposed,which is capable of reflecting the damage mechanism of the column.Meanwhile,based on the fiber model,a finite element analysis method that could simulate the critical mechanical behavior of hollow columns are proposed,establishing the basis for the evaluation of the seismic performance of the reinforced concrete frame structure adopting hollow columns.Furthermore,based on genetic algorithm,a method for determine the parameters of the lateral load-displacement relationship of hollow column under fixed axial load is proposed,establishing the basis for the researching on the concentrated plastic hinge model of hollow column.(3)The influence of the design parameters on the seismic performance of hollow column are investigated.The results indicate that with the increasing of the axial load ratio,the load-bearing capacity of the hollow column increases first and then decreases slightly.The increasing of axial load ratio significantly reduces the ductility of the hollow column.Meanwhile,the increasing of hollow ratio significantly reduces the ductility of the hollow column,while the influence of hollow ratio on load-bearing capacity is not significant.Furthermore,increasing of the section size could effectively improve the load-bearing capacity and ductility of hollow column.Based on 576 analysis cases,the simplified equations for predicting the axial force-moment interaction diagram of hollow column are proposed.The rationality and reliability of the simplified equations are validated.The simplified equations could be an important reference for the design method of hollow column and its application.(4)Based on the prototype structure,the nonlinear finite element model of RC frame structure with solid columns and with hollow columns are established,respectively.Nonlinear static analysis and time history analysis are conducted.The seismic performance of two frame are compared.The failure mode and the seismic response of RC frame structures with hollow columns are revealed.The results indicate that by replacing the solid columns in the RC frame with hollow columns,the dynamic characteristics,mechanism of damage evolution and seismic responses of the RC frame only are slightly affected.The seismic performance of the RC frame structure with solid columns and with hollow columns are approximately identical.These research outcomes provide an important reference for the application of hollow column in real engineering practices.