Influence of soil-structure interaction on fragility assessment of building structures

In this work, 3D reinforced concrete (RC) and steel building structures have been considered for studying the effect of soil-structure interaction modelling on the structural fragility assessment of such structures. In particular, three foundation models were considered: fixed model where soil-structure interaction is neglected, spring model with single-node Winkler springs and pile foundation model where soil-structure interaction is simulated using beam and quadrilateral finite elements for the pile and soil numerical simulation, respectively. For the assessment of the structural performance and the influence of the various soil-structure interaction numerical simulation models, fragility analysis is applied by considering four limit-states. For the purpose of the current study 3D, low-, mid- and high-rise RC and steel buildings are studied. The test examples employed in this study were designed first according to Eurocodes 2, 3 and 8 using the SCADA Pro analysis and design software and then nonlinear static analyses were performed for developing the fragility curves. Comparing the outcome of fragility analysis it was observed that for the case of the low- and mid-rise buildings, the structural performance was not affected significantly by the foundation system. However, it was observed that the foundation system contributes considerably to the overall structural performance of the high-rise structures examined.