SIZE EFFECTS FOOTING ON THESEISMIC PERFORMANCE OF THEMID-RISE BUILDING CONSIDERINGTHE DYNAMIC SOIL-FOUNDATION-STRUCTURE INTERACTION ANDCOMPARED WITH CONE MODEL

Shallow foundations are among the most common typesof foundations used to support mid-rise buildings in ar-eas with high seismic hazard. Recent studies have indi-cated that dynamic interaction of soil-foundation andbuilding can a ect the seismic response of structuresduring an earthquake. Therefore, the foundation fea-tures can also change the dynamic characteristics, suchas natural frequency and damping of the soil-foundation-structure system. In this research, a 14 story momentresistant frame building built on shallow foundationswith various dimensions has been considered and thethree dimensional prototype of all three components ofsoil-foundation-structure system has been modeled byABAQUS nite element software. Also modal analysiswas performed to calculate the natural frequencies ofeach model. In the present study, in nite boundarieswere applied in order to simulate free eld conditionand appropriate contact elements were used to modelthe slip and separation phenomena between foundationand soil elements. To do so, nite element direct modelswere developed. Cone model, as one of the approximatemethods that considers SFSI with practical engineeringprecision was veri ed and then applied in the series ofsimulations. An assessment procedure was applied tocheck the accuracy of Cone model as an approximatemethod in comparison with direct method. Structuralresponses including lateral deformation, drift, rotationand shear force distribution were studied for all cases in-cluding xed-base, cone model and SFSI direct models.Modal analysis implies that SFSI can reduce the natu-ral frequencies of the building. The results show thatshallow foundation size, due to the interaction betweensoil, foundation and structure, in uences the dynamiccharacteristics and seismic response of building. As aresult, engineers should carefully consider these param-eters to ensure the safety and economic seismic design.Cone Model with an appropriate engineering precision,functionality and high analysis speed is capable of assess-ing dynamic sti ness of soil due to the soil-foundation-structure interaction phenomena.