Three-Dimensional Seismic Response Analysis Of Seismically Isolated Curved Girder Bridges

As the development of moderm traffic system, curved bridges are adopted more widely. For the complexity and the particularity, research of seismic design of curved bridges is still faultiness. This thesis presents a seismic response study of curved bridges under three-dimensional earthquake excitations. And the major content is as follows:Firstly, apply the Proper Orthogonal Decomposition of the ground motion processes in the form of a spectral proper transformation (SPT), and the SPT of the 3-V 1-D ground motion processes at each point of the space defines a new set of ground motion processes components, called spectral proper components and uncorrelated for any time lag. Assuming, as seems physically reasonable, that principal components uncorrelated at one single point remain uncorrelated in different points, makes it poffible to obtain a new model of the tow-point coherence function of the different seismic ground motions components so as to complete the statistical model of the 3-V, 4-D seismic ground motions. Embedding the spectral principal components in a Monte Carlo framework, makes this model very attractive for the digital simulation of seismic ground motion.Secondly, to include the warping effect the curved beam element with eight degrees of freedom is utilized. The element stiffness matrix, element mass matrix and seismic mass matrix in three directions for both girder and pier elements have been derived. The bilateral coupled restoring force model of lead rubber bearings is introduced, and the element stiffness matrix for the bearing element can be derived from this model by the Runge-Kutta method.Finally, MATLAB program is compiled to conduct time history analysis of a three-span, continuously curved girder bridge under earthquake. Comparisons are made between three-dimensional and single-dimensional responses. It is shown that: the internal forces of structure under the three-dimensional earthquake excitation may be larger than that under the one-dimensional excitation, and seismic analysis considering three-dimensional earthquake motion must be performed for the curved grider beam.