The Seismic Response Analysis Of Three-tower Suspension Bridge

In recent years, increasing numbers of long span bridges have been built to meet the need of transportation.The suspension bridge, helped by its great capacity of span and beautiful structure, becomes a competitive bridge type among long span bridges. With the advancing modern science technology in bridge design and construct, the span of bridge is becoming more longer. Comprehensive consideration the construction cost and the technical level,multi-tower suspension project develop fast,and three-tower suspension bridge project is favoured by bridge engineer. As a new structural type, deep analysis and research has to be carried out for the large span three tower suspension bridge on static and dynamic behaviour in earthquake and selection of various restraint system for structure.Firstly, this thesis briefly introduces the basic situation of suspension bridge, the history of traditional suspension bridge and multi-tower suspension bridge home and aboard,and then introduces the research status on suspension bridge.After these the features of earthquake and importance of seismic research on bridge structure are introduced on basis of document searching. It is followed by the introduction of finite-element theory on structure dynamics and analysis method of seismic response to large span structure. Combined with structure feature of suspension bridge, the geometric non-linearity effect and the nonlinear analysis method is presented.Professional finite element software MIDAS/Civil are adopted to model the finite element space analysis separately so as to study the natural vibration of three tower suspension bridge and compare its seismic response to different restraint system. Conclusions are made as follows after comparing the calculation of model under different structure system:Large span three tower suspension bridge has a similar modal with double tower suspension bridge,which is in accordance with the general rule of typical flexible structure; the internal force of middle tower in the earthquake is larger than the side tower; combined consideration should be taken for the effects of the structure displacement and internal force caused by the earthquake when setting a central buckle between main cable and stiffening beam; the longitudinal rigid constraint and flexible constraint at the middle tower can control the displacement time history of structure. However, the rigid constraint may dramatically increase the bending moment peak of middle tower in the earthquake.