Seismic Response Analysis On A Long Span Hybrid Girder Continuous Rigid-Frame Bridge

With good mechanical behavior and mature construction technology, the continuous rigid-frame bridge has been widely used and its span is becoming larger and larger. Due to this situation, safety study on earthquake is keenly needed to carry on. This paper, based on the Xiaolan long span continuous rigid-frame bridge with hybrid girders, firstly constructs the finite element model and analyzes its dynamic characteristic with different model of bearing types, pile-soil interactions and pier heights. Secondly simulate seismic wave on the basis of the regulated response spectrum. Adopting the response spectrum method and the time-history analysis method, seismic response of the completion state and the maximum cantilever stage by using uniform inputs are calculated. Then aiming at geometric nonlinearity and crucial parameters-the bearing type, pile-soil interaction and pier height, conduct a comparison and finally attain useful results.The main work and conclusions are as follows:1. Build the finite element model of Xiaolan Bridge and detect its dynamic characters. Calculations illustrate that, the long span prestressed concrete rigid-frame bridge with hybrid girders contains a bunch of close modes, within which beam-dominant ones is the main vibration feature of low orders and mode participation mass needs more orders. Through parameters comparison, it finds that bearing styles and pile-soil interactions affect the natural vibration characteristics. And with the increase of pier height, stiffness will decline, so does the natural frequency.2. As uniform excitation of Xiaolan Bridge for the time-history analysis method, the gound motion is simulated according to the code response spectrum.3. Analysis results are approached under different bearing types, pile-soil interactions and pier heights by both the response spectrum method and the time-history method. The result demonstrates transverse direction is weakest part, and also proves that maximum response appears around the pier top, as well as the pier bottom and nearby beam, on which more attentions should be paid. As vulnerable parts, different bearing types affect the seismic response so much. And if canceling the simulation of pile-soil interactions, internal force response gets bigger. For various pier heights, the seismic response differs; the difference also exists in the2independent limb-piers. Via a series of comparisons, the selected main pier height is testified to be reasonable. In the case that symmetric structure is not available, differentiation approaches are suggested in section design, etc. Both of the time-history analysis method and the response spectrum method obtain corresponded results.4. By using the simulated ground motion as inputs, internal force of the maximum cantilever state is seriously calculated. Besides that, detailed analysis is made on key cross-sections and significant parts, which shows an unobvious geometric nonlinearity. Though calculation, it proves the necessity to use both the time-history method and the response spectrum method, and also the importance to make amutral check when dealing with the maximum cantilever stage analysis.