The seismic response of pile foundation structures with special emphasis on soil in which a rise in excess pore water pressure is anticipated was evaluated by effective stress analysis and equivalent linearization method using a two-dimensional model. A highly versatile S-D model (Stress-Density model) was used as the sand model in effective stress analysis. The two-dimensional effective stress analysis requires an enormous amount of computation time for non-linear time domain analysis including parameter settings for the soil. Accordingly, the authors determined the values of the soil properties by a simulated evaluation of the rise and accumulation of excess pore water pressure based on the results of one-dimensional effective stress analysis, and then used these values in two-dimensional total stress analysis in order to simplify the work. This comparative study on the results of the above-mentioned analysis with the results of the two-dimensional effective stress analysis confirmed that this method of analysis yields very reliable response values for use in design of structures. Although excess pore water pressure could not be evaluated even by total stress analysis in the past, the above-mentioned method enables response to be evaluated correctly for all practical purposes.
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