Research On SMA-FPS Composite Bearing And Seismic Isolation To Continuous Bridge Under Earthquakes

Since the 1990s,several strong earthquakes in the world have made people profoundly recognize the great destructive power of the near-fault earthquakes.In general,the traditional isolation device can have a good isolation performance under the far-field earthquakes.But under the action of long-term pulse of the near-fault earthquakes,the isolation device tends to produce excessive displacement and low frequency resonance even happens,which may result in damage to the isolation device or the buildings.Friction Pendulum System(FPS)is a kind of self-resetting base isolation device with high bearing capacity,high stability and high durability.Shape Memory Alloy(SMA)is a new type of functional material with unique shape memory effect,superelastic effect and high damping characteristic and is broadly concerned in the engineering field.In this paper,the FPS and SMA cable are combined to develop a SMA-FPS composite bearing.On the one hand,the SMA cable can increase the horizontal stiffness of the FPS and limit the excessive displacement of the bearing.On the other hand,the superelastic effect and the high damping characteristic can consume seismic energy and reduce the seismic response of the isolated structure.In order to study the mechanical properties and seismic isolation effect of SMA-FPS composite bearing,the main work of this paper is as follows:(1)The model of restoring force of FPS was deduced,and several kinds of the constitutive relation of SMA were introduced.On this basis,SMA-FPS composite bearing was proposed,and its working principle and components were discussed.Then,two kinds of SMA-FPS composite bearings with different cable arrangement were studied,and the formulae of restoring force were established.The two kinds of bearings were selected and compared in several aspects.In addition,the design points of SMA-FPS composite bearing were introduced.(2)Firstly,the solid models of FPS and SMA-FPS composite bearing were established by using ANSYS software.Then,the hysteretic energy dissipation characteristics and self-resetting characteristics of the two bearings were studied by simulating the low-cycle reciprocating test.Finally,the influence of design parameters such as vertical pressure,displacement amplitude,friction coefficient,curvature radius of sliding surface and cable area on the mechanical properties of SMA-FPS composite bearing were studied.(3)The finite element models of continuous beam bridge with basin bearing,FPS and SMA-FPS composite bearing were established by using Midas Civil software.Then,the dynamic characteristics of bridge structures under different bearing conditions were studied by modal analysis.And then,three typical far-field seismic waves and three typical near-fault seismic waves were selected to analyze the bridges under the three kinds of bearing conditions with nonlinear time-history analysis methods of rare earthquakes.Through analysis and comparison of the bearing displacement,the beam acceleration and the pier base moment,the seismic isolation effect of SMA-FPS composite bearing in the continuous beam bridge were investigated.Finally,the influence of SMA-FPS composite bearing design parameters on the seismic response of the bridge was studied The results show that the SMA-FPS composite bearing has good isolation performance,especially its control of the bearing displacement under the near-fault earthquake is much better than that of the FPS.