Pseudo-static Test Of High Pier Model With Self-centering Isolation

The western region of China is a high-intensity seismic area which is mountainous.Bridges with tall piers have been widely applied in these regions.Taking a railway bridge with tall hollow piers as an example,the seismic performance of self-centering rocking isolation tall hollow pier was investigated through the pseudo-static testing method,and the test was simulated based on Open Sees program package.The isolation mechanism and seismic performance of the self-centering rocking isolation tall hollow pier were analyzed via model test and numerical simulation.The research contains the following aspects:(1)The paper reviews the development of the seismic concept both from home and abroad,and main attention has been paid on Rocking Isolation Field.Achievements made by domestic and foreign scholars in theoretical calculation,numerical simulation and experimental research of the field have been collated.Several bridges designed with Rocking Isolation Concept are briefly introduced;the mechanism and the advantage of Rocking Isolation are analyzed in detail.(2)A Self-Centering high pier model with geometric similarity ratio of 1:25 was designed.The model test was divided into two working conditions: Free Rolling condition and condition with displacement-limiting bars.Two identical pier models and a five-meter I-beam were used to simulate the dead load of bridge superstructure in the experiment,and different equal-amplitude displacement loading-control systems were adopted in the working conditions.(3)Basic parameters such as hysteresis curve,skeleton curve,moment of pier,lift-off condition,effects of the restrainer bars,width of pressurized zone at the bottom of the cushion cap,corner of pier bottom,and other experimental phenomena,which reflect the isolation performance of the pier model,were obtained through the pseudo-static tests.And by comparing the corresponding experimental results of the two working conditions,the isolation mechanism and the effect of the self-centering high pier were verified.The comparison results also show that the bars can significantly reduce the displacement of pier top,postpone the lift off,increase the stiffness and ductility of the pier.(4)A numerical model of the test pier was established based on Open Sees platform.The bearing platform was simulated with the rigid arm along the bridge,the pier lifting simulated with the compression spring,and the truss element to simulate the prestressed displacement-limiting bars.The loading process of the self-centering Rocking Isolation model was simulated by numerical simulation,thus,the data of the parameters mentioned above were obtained.(5)By comparing the data obtained by the test with the corresponding numerical simulation results,it shows that Open Sees Platform can well simulate the main results which contains the hysteresis curve,the skeleton curve,the lift off condition and the effect of the limit reinforcement,attained by the pseudo static test of the self-resetting and isolation high pier.Especially,the pretty high precision of the simulated hysteretic and skeleton curves was acquired,and relatively high accuracy of the simulation of the displacement-limiting bars was also acquired.