The Analysis Of Seismic Performance Of Isolated FPS High-speed Railway Bridge Under Unidirectional And Bi-directional Seismic Excitations

With the advantages of fast, safety, comfortable, the high-speed rail had become the main development trends of traffic network. In China, various kinds of bridges in the high-speed rail have been built by adopted the method of ‘bridge replace road, bridge replace tunnel'. For the high requirements of smooth and steady in high-speed rail, the horizontal and vertical stiffness of bridge pier should be in large enough. However, China located in the world`s biggest two earthquake zones that earthquake activities were frequency, under the action of earthquake, the larger stiffness of bridge pier was more easily to be destroyed than the smaller one. Therefore, it was very necessary to adopt seismic isolated technology in high-speed rail bridge. According to the large weight of high-speed upper structure and high requirement of the horizontal displacement of bearings, the traditional rubber bearings were not suitable been used in high-speed rail because of the limited vertical bearing capacity and the problem of horizontal stiffness?durability?stability.In this paper put forward the isolated scheme of FPS ? elastic-plastic damper with displacement-constraint device in high-speed rail, and analysis the seismic behavior and parameters of bridge under the action of unidirectional seismic and bidirectional seismic. The main content shown below:1 The actual high-speed rail isolated bridge as the subject, using SAP2000 and Midas software established the bridge nonlinear model, then contrasted the natural vibration periods and model of bridge and verified the correctness of model. The bridge model that established by SAP2000 as the subject, bridge floor structure adopted elastic space beam element, FPS adopted the Friction Isolator element, bridge concrete adopted Mander model and adopted fiber element to divide, then analysis the seismic behavior of isolated bridge in horizontal direction and vertical direction respectively under the action of unidirectional seismic and bidirectional seismic. Selected 7 unidirectional and 3 bidirectional by fitted the acceleration and compared the spectrum acceleration with standard response spectrum.2 Under the unidirectional seismic action, analysis the seismic behavior of isolated bridge in horizontal direction and vertical direction respectively by adopted three isolated schemes that FPS?FPS with damper?FPS with damper and displacement-constraint device, then verified the validity of the isolated scheme in this paper, ensured the safety of the isolated bearing based on ensured the isolated effect of bridge.3 Analysis the parameter effect of the three isolated schemes, supposed the selection rules of the parameter of the three isolated schemes. By lots of simulated analysis obtained the reasonable parameter values of FPS`s frictional coefficient and radius?elastic stiffness of elastic-plastic damper?plastic stiffness?stiffness ratio?limited distance of displacement-constraint device?elastic stiffness.4 Under the bidirectional seismic action, analysis the seismic behavior of isolated bridge in horizontal direction and vertical direction respectively by adopted the three isolated schemes that FPS ? FPS with damper ? FPS with damper and displacement-constraint device. It was pointed that compared with bidirectional earthquake the unidirectional underestimated the displacement of bearing, so there were safety hidden trouble in actual. Therefore, it is necessary to consider the action of bidirectional earthquake in the research and application of isolated bridge..