Non-Stationary Stochastic Seismic Responses Analysis Of Long-Span Composite Girder Cable-Stayed Bridge

The rapid development of the cable-stayed bridges has been more important in the traffic system.With the increasing span, seismic researchs of long-span cable-stayed bridge has become the concerned issue by all communities. Due to the uncertainty of the earthquake,the stochastic method is more reasonable. In this thesis, using a general finit element software ANSYS combined with absolute displacement solving method and pseudo excitation method analyzes the random seismic response of the composite beam cable-stayed bridge under multi-dimensional and multi-support earthquake excitations. The main contents as follow:1. It introduces the random of the ground motion input seismic spectrum model and seismic spatial effect model.Contrast the differences between the traditional pseudo excitation method and absolute displacement solving method. The latter improves heavily the efficiency of stochastic vibration method.2.By establishing a finite element model of Guanyinyan Bridge,and analyzes the dynamic characteristics,understand its vibration mode distribution characteristics,and further to determine the stiffness characteristics of salt bridge for the instruction of design.3.Using ANSYS combined with pseudo excitation method based on absolute displacement solving analyzes the random seismic response of the composite beam cable-stayed bridge under multi-dimensional and multi-support earthquake excitations.By the response power spectrum,it analyzes the seismic response of Guanyinyan Bridge under the non-uniform excitations. By considering traveling wave effect,it is unfavorable for the displacement of the main girder,but favorable for the main tower. The results obtained by considering partial coherent effect are slightly reduced,contracting the uniform excitation,and it has has a significant effect on the structural response without considering coherent effect. Considering local site effectits seismic responses have less change.4.It introduces the theory and realization method of non-stationary seismic excitation,which is based on absolute displacement solving method.Analyze the seismic response of Guanyinyan Bridge under the uniformly and non-uniformly non-stationary seismic excitations. The non-stationary response of seismic ground motion is reduced about 20% than the stationary response. Considering the non-stationary effect,the response has a significant effect on the initial stage of earthquake, and the stationary phase is slightly decreased, and the attenuation stage is basically consistent.