Research On Seismic Response And Spatial Variable Effects Of Ground Motions Of Long Span Bridges

Taking account of the present status of seismic response on large span bridge structures, in this paper, a new time-history analysis method is proposed based on the combination of Large Mass Method Theory and Clough Pseudo Static Displacement Theory, the equation of motion is derived, and the practical numerical method of this new theory is obtained. Comparing with the elder time-history theory of relative displacement, this new time-history theory can get the absolute displacement of structures by taking the translation of ground base into account. After this, based on the large amount research of predecessors, a new seismic power spectrum density model is proposed to match the applicable codes of seismic design of road engineering. Different kinds of spatial variability effects and nonstationarity of ground motion are considered in this model and the model can be operated conveniently as substitute of the traditional response spectrum method. Then three engineering examples are analyzed, three seismic response analysis methods are adapted, accurate finite element model is established, and numerical analysis is performed based on the absolute displacement time-history theory and stochastic seismic power spectrum density model which are proposed in this paper. The analysis result proofed the rationality and feasibility of the theories proposed in this paper. At the meantime, the finite element modeling method, dynamic characteristics and seismic response characteristics of different kinds of large span bridges are explored, and the spatial variability effects of ground motion are studied in detail. The study shows that the spatial variability effects present significant influence on the seismic response especially the wave-passage shows a great affect. However, to different kind of large span bridge, the effect of wave-passage varies. To different case, the analysis should have different result.