Urban Scale Fragility Assessment of Structures Considering Soil-Structure-Interaction

Abstract

Fragility curves for structures are typically calculated considering fixed-base structures, i.e., neglecting the interaction between soil, foundation, and structure (SFSI). The state-of-the-art literature proves that considering foundation flexibility, especially for structures resting on soft soil, may lead to different fragility or loss estimates than the fixed-base-on-rock assumption. Including these effects on the city-scale vulnerability analysis is considered a challenging task due to the high exposure concentration and complexity of all the interacting urban systems. For this reason, large-scale analyses are commonly carried out applying existing fragility curves which may have been assessed not correctly accounting for the variation in frequency and amplitude contents imposed by each site’s local geotechnical and topographic conditions. To this aim, a new simplified methodology is proposed in this study to perform an urban-scale vulnerability assessment of structures considering the influence of SFSI and local site-effects. The applicability of the proposed approach is based on globally available data regarding the soil parameters, the foundation, and the building taxonomy. The main findings demonstrate that the conventional way of calculating fragility curves may lead to an incorrect evaluation of the seismic risk, especially in soft soil formations.