Study On Seismic Behavior Of RC Pier Columns Under Different Loading Paths

As the main load-bearing and lateral force resisting components of bridge or building structure,the seismic performance of RC pier is different due to the different cyclic loading history of quasi-static test.Due to the limitation of the randomness and complexity of the earthquake action and the test conditions,the study on the influence of quasi-static loading system(such as the number of cycles and the magnitude of displacement,etc.)on the performance of the pier column is not enough,and the quasi-static loading system(path)which reasonably reflects the real earthquake action needs further study.Therefore,based on the methods of test and numerical simulation,this paper focuses on the influence of different loading paths on the mechanical mechanism and seismic performance of pier column members.The main research contents are as follows:(1)Through the quasi-static test of nine RC square columns,the influence of different axial compression ratio and loading cycles on the seismic performance of pier columns under monotonic loading and variable amplitude cyclic loading(3 and 10 cycles for each amplitude)is studied.The results show that with the increase of axial compression ratio,the peak load of pier increases,while the ductility coefficient of displacement decreases.Under the cyclic load of variable amplitude,the seismic performance of RC pier after peak load decreases with the increase of load cycles.(2)The quasi-static tests were carried out on six piers with different loading paths(variable amplitude loading with different increment of displacement amplitude,different cycles under the same level of displacement and progressive decrease of displacement amplitude).The influence of pseudo-static loading paths on the seismic performance of piers was studied.The results show that with the increase of displacement amplitude after yielding,the ductility coefficient of pier increases and the energy dissipation capacity decreases.Compared with the multiple cycles of small displacement amplitude after yielding,the deformation and energy dissipation capacity of pier columns under multiple cycles of large displacement amplitude are significantly reduced.Due to the effect of large displacement amplitude,the peak load and the energy dissipation capacity of the pier will be significantly reduced when the first cycle of the pier is reversed loaded.(3)Based on the fiber model theory,considering the action of bond slip,an analysis model of the stress and deformation of the macro element of the pier column is established.Based on the model,the test results of this paper are analyzed.The calculated results(load displacement curve,bearing capacity and bearing capacity degradation at the later stage of loading)are in good agreement with the test results.The model in this paper can reflect the influence of different loading paths on the seismic performance of pier columns,and it is suitable for nonlinear analysis of pier columns under complex seismic loads considering cyclic degradation effect.(4)Based on the numerical model proposed in(3),the influence of different loading cycles and displacement amplitude increment on the seismic performance of pier columns under horizontal two-way loading path is analyzed.The results show that: compared with the one-way load,the horizontal bearing capacity of the pier under the two-way load is significantly reduced,the deformation capacity and energy consumption are significantly reduced;the influence of the number of cycles and the increment of displacement amplitude on the seismic performance of the pier under the two-way load is more significant.