| Reinforced concrete(RC)short columns are prone to shear failure under strong earthquake,which affects the overall safety of reinforced concrete frame structure.Scholars at home and abroad have conducted a lot of research on them.At present,the research on RC short columns is mainly focused on the main axis loading direction,the axial pressure is relatively small,and the reinforcement measures for the brittle failure of short columns are less.In this paper,the seismic behavior of RC short columns with high-strength longitudinal bars under the action of high axial compression ratio oblique load is studied by the method of experimental study and numerical simulation,and the strengthening measures are proposed.The main work and results are as follows:Six RC short columns with high-strength longitudinal reinforcement were subjected to low-cycle repeated loading tests under high axial compression ratios under diagonal loads.The failure mode,hysteretic curve,bearing capacity,deformation energy,stiffness and energy dissipation performance of the specimens were studied.The effects of loading angle,axial compression ratio,densely packed high-strength stirrups,carbon fiber reinforced plastic(CFRP)constraints,and steel plate net constraints on the seismic performance of RC short columns are analyzed.According to the material properties of various materials measured in the test,OpenSees software is selected to model the specimen reasonably by selecting appropriate material constitutive relation,stress unit,section division,etc.,to simulate the hysteretic performance of RC short column under various test conditions,and to compare with the test results.The results show that compared with the horizontal load,the corner concrete of the RC short column in the loading direction under the diagonal load is subjected to two-way load,which causes serious damage,the bearing capacity of the test specimen becomes worse,and the stiffness is severely degraded.The increase of axial compression ratio under the action of oblique load makes the concrete of the specimen fall off in a large area,the damage is more serious,the bearing capacity is increased,but the deformation capacity is reduced,the rigidity degradation is serious,the specimen is prone to brittle failure,which is not conducive to the seismic performance of the specimen.Compared with ordinary stirrups,the specimens with dense high-strength stirrups have less inclined cracks,less damage,full hysteretic curve,improved the strength and energy consumption capacity,and the specimens change from shear failure to bending shear failure.This is mainly because dense high-strength stirrups provide strong lateral binding force for concrete and high-strength longitudinal bars,and give full play to the properties of high-strength bars.On the basis of dense high-strength stirrups,the winding of CFRP at the end of the column limits the development of diagonal cracks and improves the strength and energy consumption capacity of the specimen,but the sudden fracture of CFRP at the end of the column causes the failure of the specimen earlier,and the improvement of its deformation capacity is not significant.On the basis of dense high-strength stirrup,the steel plate net is wrapped around the column end,which improves the restraint degree to the concrete at the column end,limits the development of diagonal crack,the hysteretic curve of the specimen is full,the strength,deformation capacity and energy consumption capacity are improved,and the shear failure of the specimen changes to the bending shear failure,which shows that dense high-strength stirrup and steel plate net at the column end can effectively improve the short length of reinforced concrete The seismic performance of columns under the action of high axial compression ratio and oblique load,and the combination of dense high-strength stirrups and steel mesh at the end of columns can improve the seismic performance better.In addition,the OpenSees finite element program can simulate the hysteretic behavior of high-strength RC short columns under high axial compression ratio and oblique load by selecting material constitution,section restoring force model and stress element reasonably. |
