Seismic Performance Of Tubed Reinforced Concrete Frame Structures

The steel tube confined concrete column has a strong confinement effect with advantages of high bearing capacity,good seismic performance,high fire resistance,a full use of high-strength materials,saving formwork and convenient construction.There are good engineering application prospects in large-span bridges,heavy loads or super high-rise buildings.At present,the research on steel tube confined reinforced concrete structures mainly focuses on column components and connections,but there are relatively few researches on their structural systems.In this paper,the seismic performance of steel tube confined reinforced concrete column-RC beam frames was studied by experimental testing and finite element simulation analysis.The main research work and results are as follows:(1)Using the column-beam strength ratio as a control parameter,2 two-story,two-span circular steel tube confined reinforced concrete column-RC beam frames were tested under the pseudo-static hysteretic loading.Through the test,the load-lateral displacement hysteresis curves,skeleton curves,stiffness degradation curves,stress in rebar-displacement curves,stress in steel tube-displacement curves were recorded.The lateral resistance and deformation capacity of the frames were analyzed.The deformation mechanism,energy consumption performance,stiffness degradation and failure mechanism of the frames were discussed.From the results of the pseudo-static test,typical beam hinge and column hinge failure mechanisms respectively appear in frames that meet and break through the limit requirements of "strong column and weak beam" design philosophy.(2)The ABAQUS software is employed to establish a refined solid finite element model of the steel tube confined reinforced concrete column-RC beam frame,which is verified by comparing the predicted load-displacement skeleton curves with the test results.Based on the finite element model,the seismic behavior of the test frames under the whole loading process is simulated to investigate the stress development process and elastoplastic deformation and load-carrying mechanism of the structure.The influence of the floor on the RC beam and the rotation of the beam-column joint on the seismic performance of the steel tube confined reinforced concrete frame was analyzed.(3)The Open Sees software is employed to establish a fiber-based numerical model of the steel tube confined reinforced concrete column-RC beam frame,which is verified through the load-displacement hysteresis curves,energy dissipation curves and the deformation mode measured by the experiments.Based on the fiber-based numerical model,parameter analysis is carried out to study hysteretic performance of the frames,including compressive strength of concrete,yield strength of steel tube,diameter-to-thickness ratio of steel tube,axial compression ratio,beam-column stiffness ratio,length-diameter ratio and column-beam strength ratio.The influence of the studied parameters on the seismic performance of frames is determined,based on which the corresponding design suggestions are proposed.(4)Using the fiber-based numerical model,an eight-story steel tube confined reinforced concrete frame under 8 degrees of seismic intensity(0.20g)was designed and the static Pushover analysis was carried out.The seismic behavior of the frame structure under a small,a mediun,and a large earthquake was investigated.The floor displacement,inter-story drift ratio,and plastic hinge development of the frame structure is assessed.