Site response analysis is commonly performed to account for local site effects on ground motion propagation during an earthquake. Most site response analyses involve horizontal ground motion, considering vertically propagating shear waves in horizontally layered systems.
In reality, the ground is simultaneously subjected to shaking in both the horizontal and vertical direction during an earthquake, but the vertical response has received limited attention in the literature. Field evidence from various recent earthquakes indicates though that damage of concrete buildings and bridges can be attributed to high vertical ground motion, while the vertical component is also important for the design of critical facilities such as nuclear power plants and offshore wind turbines.
The talk will first give an overview of fundamental aspects of vertical site response analysis, demonstrating the impact of parameters characterising the hydraulic phase, i.e. soil permeability and pore fluid compressibility, on vertical site response predictions in terms of both frequency content and amplification.
A practical methodology will be presented which allows the direct use of existing site response software, originally developed for propagation of shear waves, to perform site response analysis for vertical ground motion. Finally, the impact of the vertical component of ground motion will be demonstrated in three-dimensional analyses for a KiK-net down-hole array in Japan, comparing the numerical predictions against field measurements.
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