Development of a two dimensional, stochastic methodology to assess seismic site response

Student: Andres Felipe Alonso Rodriguez
Supervisors: Dr Carlo Giovanni Lai


Site effects are crucial for seismic risk assessment of structures; but in order to perform a reliable analysis, two major facts should be considered: variability of soil mechanical properties along all directions; and, effects of topographical and morphological features that might overcome traditional, one dimensional analysis procedures. In order to address these, a two-dimensional, stochastic assessment methodology to estimate site effects has been developed. This procedure allows for geostatistical interpolation of mechanical properties of the soil underlying a site, based on field measurements of shear wave velocity data at specific locations. Afterwards, Montecarlo simulations and First Order, Second Moment (FOSM) estimates are performed on a two dimensional finite element mesh to assess variability of surface response, represented by their mean and standard deviation, at several places on top of a profile which includes the side. The methodology has been successfully tested for two artificially generated custom sites, in agreement with FEMA 450 specifications for geotechnical research. Effects of different statistical descriptions of soil properties, sampling strategies, and finite element modelling strategies were reviewed for these cases, yielding some general remarks.

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