The Wavelet Method For Seismic Response Analysis Of Large-span Structures

For large-span structures, we can not ignore the impact brought by the traveling wave effect in the calculation of seismic response. Meanwhile, in previous studies, it is generally agreed that horizontal seismic action is the main cause of earthquake disaster and underestimat the impact of the vertical seismic action on the structure. Wenchuan earthquake left us a rich original seismic data records, and by contrast, the peak acceleration of V wave component is greater than the NS wave component.The research on multi-input and multi-dimensional under the action of actual seismic records is significant.The main work and achievements are as follows:(1)From earthquake waves database, we select Wolong seismic waves and Baoji seismic waves,in which we choose NS and V components as the input waves, then we decompose the waves into different frequency bands wavelet components using Bspline wavelet, as the input seismic wave.of multi-input and multi-dimensional excitation for time history analysis. Traveling wave effect is treated as the main factor to calculate the seismic dynamic response of large-span structure. The formula of displacement, equivalent static and equivalent static bearing about multi-excitation and uniform excitation are derived.(2)A large-span structure with two span is chosen as a model, and the beam-column nodes is defined rigid and hinged. Matrix displacement method and static condensation are used to generate a stiffness matrix for large-span structure and mass matrix is generated by lumped mass method.The damping ratio is 0.5 for architecture. Using the time history analysis of multi-excitation and uniform excitation, wavelet components of seismic waves of Wolong seismic waves and Baoji seismic waves, the displacements of the large-span structures is calculated. On this basis, displacement about wavelet components of the original wave and the band is researched. The program is drawed up and the data is computed by MATLAB.(3)By contrast,the natural frequencies for rigid nodes is higher than for hinged nodes. Therefore,by analysing the displacements of rigid nodes with hinged nodes for the large-span structure, we can obtain : first, for rigid nodes, the horizontal displacements in uniform excitation is higher than in multi-excitation,however,the vertical displacements do not have a regular pattern; for hinged nodes,the horizontal and vertical displacements in uniform excitation is always higher than in multi-excitation. second, the impact of traveling wave effect in hinged nodes is weaker than in rigid nodes. After considering the impact of traveling wave effect, the contribution of higher modes for displacements increases, and the impact of higher modes on the vertical displacement is significantly higher than the impact on the horizontal displacement.third, in identical input and non-uniform input, the horizontal displacement are mainly affected by the first-order modes,while vertical displacements are determined by beam-column constraint,in rigid nodes, the vertical displacement is mainly affected by the top three vibration modes,in hinged nodes, vertical displacement is mainly affected by the second and third modes.(4)Wolong seismic waves have more high-frequency components of seismic waves than Baoji seismic waves. By comparing the displacements of inputing Wolong waves with Baoji waves for the large-span structure, we can obtain:Higher modes after inputing Wolong waves have a higher proportion than after inputing Baoji waves. Compared with Wolong waves, the displacements differences between multi-excitation and uniform excitation after inputing Baoji waves tend to decrease.