The spatial variation of seismic ground motions denotes the differences in the seismic time histories at various locations on the ground surface. This text focuses on the spatial variability of the motions that is caused by the propagation of the waveforms from the earthquake source through the earth strata to the ground surface, and it brings toge

[Truncated abstract] The research carried out in this thesis concentrates on the modelling of spatial variation of seismic ground motions, and its effect on bridge structural responses. This effort brings together various aspects regarding the modelling of seismic ground motion spatial variations caused by incoherence effect, wave passage effect and local site effect, bridge structure modelling with soil-structure interaction (SSI) effect, and dynamic response modelling of pounding between different components of adjacent bridge structures. Previous studies on structural responses to spatial ground motions usually assumed homogeneous flat site conditions. It is thus reasonable to assume that the ground motion power spectral densities at various locations of the site are the same. The only variations between spatial ground motions are the loss of coherency and time delay. For a structure located on a canyon site or site of varying conditions, local site effect will amplify and filter the incoming waves and thus further alter the ground motion spatial variations. In the first part of this thesis (Chapters 2-4), a stochastic method is adopted and further developed to study the seismic responses of bridge structures located on a canyon site. In this approach, the spatially varying ground motions are modelled in two steps. Firstly, the base rock motions are assumed to have the same intensity and are modelled with a filtered Tajimi- Kanai power spectral density function and an empirical spatial ground motion coherency loss function. Then, power spectral density function of ground motion on surface of the canyon site is derived by considering the site amplification effect based on the onedimensional seismic wave propagation theory. The structural responses are formulated in the frequency domain, and mean peak responses are estimated by the standard random vibration method. The dynamic, quasi-static and total responses of a frame structure (Chapter 2) and the minimum separation distances between an abutment and the adjacent bridge deck and between two adjacent bridge decks required in the modular expansion joint (MEJ) design to preclude pounding during strong ground motion shaking are studied (Chapter 3). The influence of SSI is also examined (in Chapter 4) by modelling the soil surrounding the pile foundation as frequency-dependent springs and dashpots in the horizontal and rotational directions. A method is proposed to simulate the spatially varying earthquake ground motion time histories at a canyon site with different soil conditions. This method takes into consideration the local site effect on ground motion amplification and spatial variations. The base rock motions are modelled by a filtered Tajimi-Kanai power spectral density function or a stochastic ground motion attenuation model, and the spatial variations of seismic waves on the base rock are depicted by a coherency loss function. The power spectral density functions on the ground surfaces are derived by considering seismic wave propagations through the local site by assuming the base rock motions consisting of outof- plane SH wave and in-plane combined P and SV waves with an incident angle to the site. The spectral representation method is used to simulate the multi-component spatially varying earthquake ground motions...

The proceedings contain contributions presented by authors from more than 30 countries at EURODYN 2002. The proceedings show recent scientific developments as well as practical applications, they cover the fields of theory of vibrations, nonlinear vibrations, stochastic dynamics, vibrations of structured elements, wave propagation and structure-borne sound, including questions of fatigue and damping. Emphasis is laid on vibrations of bridges, buildings, railway structures as well as on the fields of wind and earthquake engineering, repectively. Enriched by a number of keynote lectures and organized sessions the two volumes of the proceedings present an overview of the state of the art of the whole field of structural dynamics and the tendencies ot its further development.

This book addresses applications of earthquake engineering for both offshore and land-based structures. It is self-contained as a reference work and covers a wide range of topics, including topics related to engineering seismology, geotechnical earthquake engineering, structural engineering, as well as special contents dedicated to design philosophy, determination of ground motions, shock waves, tsunamis, earthquake damage, seismic response of offshore and arctic structures, spatial varied ground motions, simplified and advanced seismic analysis methods, sudden subsidence of offshore platforms, tank liquid impacts during earthquakes, seismic resistance of non-structural elements, and various types of mitigation measures, etc. The target readership includes professionals in offshore and civil engineering, officials and regulators, as well as researchers and students in this field.

Adjacent bridge structures can move relatively to each other in an earthquake, resulting in pounding or more severely, unseating. Pounding occurs when the relative closing movement is larger than the structural gap whereas girder unseating takes place due to the relative opening movements being larger than the seating length provided. Relative displacements arise from unequal fundamental frequencies of adjacent bridge structures, spatial variation of ground motions and different soil-structure interaction (SSI). The objective of this thesis is to investigate the influence of these factors, especially spatial variation of ground motions on the bridge response. To achieve the objective, a series of experiments were conducted on the bridge models made of polyvinylchloride (PVC) using either shake tables or inertial actuators. Ground motions of the soft soil, shallow soil and strong rock conditions based on the New Zealand design spectra were simulated. The ground motions of the soft soil condition were further classified as highly, intermediately and weakly correlated ground motions to account for coherency loss effect of excitation spatial variation. These experiments include testing a 1:125 scale bridge with three identical bridge segments to study the effect of spatially varying ground motions with pounding, testing the same model but with the footings on sand contained by rubber boxes to consider the effects of spatially varying ground motions and SSI with pounding, testing one of those bridge segments with movable abutments to investigate the effect of excitation spatial variation considering abutment excitation and pounding, testing a 1:125 scale bridge model with two identical bridge segments with artificial plastic hinges to study the effect of spatially varying ground motions on inelastic bridge response with pounding, and field testing a 1:22 scale bridge segment subjected to spatially varying ground motions to determine the minimum total gap of a modulus expansion joint required to avoid pounding. A total of 8660 tests were performed. Research found that spatial variation of ground motions can increase the relative displacement of adjacent bridge girders and pounding forces. Based on the experimental results, the New Zealand Transport Agency (NZTA) Bridge manual was reviewed. It was found that the current NZTA Bridge manual is unable to suggest sufficient minimum seating length to accommodate the measured relative opening displacements. A set of empirical equations is therefore proposed to calculate adequate minimum support seating lengths to prevent girder unseating.