Seismic Response Analyses Of The Changshan Extradosed Cable-stayed Bridge Considering Soil-structure Interaction

Short tower cable-stayed bridge is an new type of bridge in recent decades and has demonstrated huge potentials due to its unique aesthetical features and flexible span arrangement as well as its sound economic performance. Short tower cable-stayed bridge has a stress characteristic between continuous bridge and cable-stayed bridge, and there are also relations and differences between short tower cable-stayed bridge and these two types of bridges in terms of dynamic characteristic and earthquake response. Hence, how to conduct accurate and precise 3D numerical analysis on its earthquake dynamic response plays an important guiding role and has a great significant reference in engineering design and engineering practice.The thesis takes the prestressed cable-stayed bridge crossing over Changshan Islands of Dalian city as the engineering background. From the perspective of entire interaction system, seismic analyses of the bridge structrue is conductued by using the commercial FEM pakage ADINA, including dynamic modal analysis, earthquake response spectrum analysis and time history analysis with step-by-step time integration method. The interaction between pile and soil is also considered in the large-scale 3D numerical FEM model. The specific content of this dissertation includes the following:(1)Equivalent static analysis of the bridge structure under gravity and lane load is conducted to make a rational evalutaion of the strength and stiffness of the bridge compared with requirements of standards. Then, the whole bridge structure is further analyzed to discuss the effects of pile-soil interaction on the dynamic inherent characteristic by employing the subspace iteration method.(2)Peak responses and from earthquake response spectrum of the bridge structure to different PGA(Peak Ground Acceleration) are provided based on the SRSS and CQC rules of modal combination method respectively. Effects of calculated mode shapes, pile-soil interaction and dimensions of seismic excitation as well as modal combination method on the computational results are discussed.(3)Both 3D elastic and elasto-plastic time history analyses under seismic excitations based on three typical earthquake acceleration records are conducted considering pile-soil interaction. From comparative analyses of results of spectrum response and time-history methods, effect of material nonlinearity of reinforced concrete is discussed in detail. Finally, the evaluation of anti-seismic performance of bridge structure is further conducted systematically.