Abstract
It is commonly accepted that multi-scale structures are subject to spatially variable seismic motions. This spatial variability of seismic motions is described by different intensities at different locations due to the coherency loss effect, wave passage effect and local site conditions. For multi-scale structures, the estimation of seismic excitations must consider these factors. Often, the influence of the spatial variability of seismic motion on the dynamic response of structures is performed by neglecting the site effect. In several cases, it has been observed that the high intensities of seismic motion are caused by the site amplification besides coherency loss and wave passage effects. This study aims to analyze the impact of local site conditions on seismic motions. For this purpose, a method of simulation of spatially variable seismic motions is performed. The seismic signals on the bedrock are defined by considering a target power spectral density and a coherency loss model. According to the seismic wave propagation theory, the projection of these seismic motions on the surface is realized. The results of this study show that neglecting the local site conditions induces an undervaluation of spatially variable seismic excitations.
Highlights
Seismic ground motions at different sites on the surface are inevitably different due to seismic wave propagation from the source to the site
This spatial variability of seismic motions is described by different intensities at different locations due to the coherency loss effect, wave passage effect and local site conditions
The influence of the spatial variability of seismic motion on the dynamic response of structures is performed by neglecting the site effect
Summary
Seismic ground motions at different sites on the surface are inevitably different due to seismic wave propagation from the source to the site. The spatially variable seismic motions are induced by three separate effects [1]. The coherency loss effect is the second factor, which results from random differences in the amplitudes and phases of seismic waves. The last factor is the site effect, which due to the spatial variation of the local soil profile characteristics that affect the amplitude and frequency content of the seismic wave. For multi-scale structures like bridges, the spatial variability of seismic ground motion can significantly affect the seismic response generated internal forces. The assumption of uniform ground motion at all supports of a multi-scale structure cannot be considered valid [2,3,4,5,6]
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