Study On Seismic Response Of Large Span Structures

The large span structure buildings are mostly important or landmark buildings.Once the Large span structure sufferred from Earthquake, the consequences of it is more serious than ordinary buildings.So it is of practical significance to study the seismic resistance of large span structures.With the extensive application of large-span structures, the technical complexity of large span structure, the higher performance of the seismic performance of long-span structures is proposed. Furthermore, it is an important feature at the seismic analysis of large span structure, that the random temporal and spatial variation during the ground motion propagation process can cause not only the changes in spectral characteristics,but also the differences earthquake excitation of the support. In the all, it is much need to focus on research to the seismic response in multidimensional multipoint excitation. In this paper,using Matlab software to establish a simplified model of large span structures based on wavelet methods,seismic wave was divided into different wavelet components that is tight adjacent different frequency bands.The wavelet analysis method is used to study the seismic response of large-span structures under multidimensional and multi point excitation.The main work of this paper is as follows:(1)In the Wencuan earthquake database, selecting Hongya seismic wave and Lixian Muka seismic wave whose earthquake acceleration response spectrum close to the design response spectrum that is designed according to site conditions. Justing the amplitude of the two ground motion time history according to the specifications. Wavelet decomposition method is applied to two seismic wavelet decomposed into nine wavelet frequency bands. Making the acceleration time history curves and Fourier spectrum pertaining two primary seismic waves and nine bands wavelet components(2) Using MATLAB to calculate the basic characteristics of the large span structure simplified model, including the mass matrix, considering static condensation of the stiffness matrix and the influence matrix,natural frequency and modal participation factors;Based on the traveling wave method,time history analysis method, modal analysis method and structural dynamics knowledge,the formula of vertical multi point excitation and multi-point excitation and multidimensional uniform excitation of long-span structure to calculate seismic response were derived.The displacement and equivalent static of Large span structure stimulated by wavelet spectrum component of Hongya and muka wave in three vertical multipoint excitation wave velocity, multi-dimensional earthquake excitation were calculated. Solving large-span structure’s the displacement and the equivalent static force in multidimensional multi point excitation and multidimensional uniform excitation. The seismic response of the large span structure under the action of different frequency bands of the wavelet component and the The wavelet component playing a leading role in earthquake response were studied, studying the contribution of the large span structural displacement quasi static and dynamic parts to the total displacement under different frequency bands and to study the influence of the velocity on the large span structure displacement and the equivalent static force.(3) The contribution of pseudo static part to the total displacement of large span structure is not always increasing the total displacement.With the wave velocity increase pseudo static contribution of large span structure displacement increases gradually, the dynamic part of the contribution to the total displacement of large span structure is gradually reduced, but the contribution of the dynamic part to the total displacement has been dominated.Under the action of different frequency band wavelet components,the influence of wave velocity on the large span structure displacement and equivalent static force is mainly reflected in the displacement and the equivalent static maximum value and the maximum value of the node changes, under different wave velocity excitation, the large span structure displacement and the equivalent static maximum gap are more than 10%.(4) The analysis and calculation results show that: The displacement maximumof large span structure under vertical multi-point excitations at different frequency wavelet vertical components smaller than multidimensional and multi point excitation.The equivalent static maximum value of the large span structure under the vertical excitation smaller than multidimensional and multi point excitation.As an example large span structure simplified model, using the wavelet analysis studying Hongya waves and Lixian Muka waves wavelet component acting on large span structure in three kinds of velocity, in the calculation of the difference of structural displacement and equivalent static force under unidirectional multi-point excitation and multi-dimensional and multi-point excitation and the difference of structural displacement and equivalent static force under multidimensional uniform excitation and multi-dimensional and multi-point excitation.The maximum value of displacement and the equivalent static force under the multi-dimensional and multi point excitation are larger than the maximum value of the displacement and the equivalent static force under the multidimensional uniform excitation.The difference of the maximum value of structural displacement and the equivalent static force of different wave velocity is larger,and the node of the maximum value of the structure equivalent static force will be changed.The maximum of large span structure displacement is under the 0~0.391 Hz frequency band wavelet components,the equivalent static force of the large span structure under the vertical multi-point 0~6.25 Hz frequency band wavelet component is larger. The wavelet component of the 0~6.25 Hz frequency band,which contains the first five order natural frequencies, plays a leading role in the large span structure displacement and equivalent static force.