Analysis And Modeling Of Spatial Characteristic Of Seismic Ground Motions

The spatial variation of seismic ground motions or SVSGM has a significant effecton long and large-span structures. It is of great importance to summarize thespatialcharacteristics of seismic ground motions and it is also difficult to be taken intoconsideration in engineering practices reasonably.Although there is plenty of successful work made in the field of SVSGM. However,the consideration of SVSGM remains in the stage of ‘wave passage effect’ inengineering practices. In order to provide some useful reference in engineering practices,the aim of this dissertation focuses on engineering practices. And in this thesis, threeaspects including characteristics of the spatial variation of seismic ground motions,modeling description methods and multi-point seismic ground motion simulations willbe discussed and researched at different levels. The main contents of this thesis include:1.Data from three seismograph arrays is collected and analysed includingSMART1Array, USGS Parkfield Array, ZG Xishan Array, and the corresponding arrayinformation, seismic ground motion data information as a research-based spatialvariation effects. Using stochastic signal processing methods to analyses data of eacharray,among them are the estimated values of coherence functions of different stations.This work is the preparation for the following study.2. The spatial characteristics of seismic ground motions based on the informationcollected in this thesisare qualitatively analyzed and discussed. The change rule ofcoherence function is studied with frequency and separations.The result pointed out thatthe coherence function decreased with the increase of frequency and separations.However, the characteristics of the coherence function of different array is not the same.The influencing factors of the discrepancy of the coherence function between differentarrays are discussed.3.The applicability of four representative coherence function modelsisdiscussed.Through the actual coherence function fitting,the results shows that themulti-parameter coherence function models, such as H-V Model and Qu Model, haswider applicability compared with double parameters or single parameter models, andalso better fitted.Statistical analysis aboutparameters selection of the H-V Model and QuModel are made using the method learned from the study of response spectrum. And therecommendation of these two models are given respectively considering different degree of coherence levels.4. In the view of engineering application, a practical synthetic method ofmulti-point ground motion input has been proposed by summarizing methods proposedbefore.Two different synthetic routes based on different initial conditions, referringtostandard seismic ground motions or power spectrum models, are given. And apreliminary test is made by an example analysis.Finally,the limitation of the research as well as the suggestions to the follow-upwork is discussed.