Analysis Of Multi-input Seismic Response For Aqueduct Structure On Different Soil Site

The seismic input is the precondition and base of structural response. It is assumed in the conventional coherent-vibration input that all of the support points have the same ground movements, while carrying on the analysis of the large aqueduct structure to response of earthquake. This is equal to treat foundation as rigid body. If the structural size is far smaller than the wavelength of earthquake, this kind of hypothesis can be accepted. Actually, because the difference of the seismic character and geology and seismic transmission, the ingoing seismic wave is variable on the time and space, even other conditions are completely consistent, the time which each support point of aqueduct receive seismic wave is fall behind each other, because the distance of support points to the focus of earthquake is different, in same time, the movement which received by each support point is different, this is the question of multi-support seismic input. Using ANSYS soft ware and basing on the model of a big aqueduct, in this paper,the author founds a seventeen-span model. Basing on the modal analysis of the structure, according to Ansys Parameter Design Language, the program of coherent-vibration input and multi-support seismic input are compiled. Using these programs, this paper calculates the dynamic response of model. In the program of multi-support seismic input, the difference of the soil site is simulated by changing the record of the seismic wave. The results of the modal analysis shows that: the natural period is almost the same as the predominant period of seismic wave, the first ten modes of vibration are lateral. For the dynamic analysis, when the record of the seismic wave is inputed to the structure on longitudinal and transverse direction ,the result of multi-support input is larger than coherent-vibration input for displacement and moment. When the record of the seismic wave is inputed to the structure on vertical direction ,the result of multi-support input is smaller than coherent-vibration input for acceleration and internal force.Considering the difference of the soil site, multi-support inputing the record of the seismic wave make the results decrease.The results show that the change of the mothod of seismic wave inputing influence the dynamic result of the structure significantly, we should analyse the actual problem in order to get rational result...