seismic evaluation of flexible-base low-rise steel frames using beam-on-nonlinear-winkler-foundation modeling of shallow footings

Recent studies have revealed that the influences of soilstructure interaction (ssi) can be detrimental to the seismic behavior of structure, and hence ignoring this phenomenon in analysis and design may result in to an unconservative design. the aim of this paper is to quantify the effects of nonlinear ssi on the seismic response of a lowrise special moment frame subjected to a family of ground motions with three hazard levels. to this end, seismic behavior of a 5story special steel frame founded on linear and nonlinear flexiblebase foundations are compared to the conventional fixedbase frame counterpart. the wellknown beamonnonlinearwinklerfoundation (bnwf) approach is employed to model nonlinear soilshallow foundation. nonlinear static and time history dynamic analyses were conducted applying the opensees platform in order to inquire the effect of modeling and ground motion parameters on their seismic performance. the results manifested some degrees of inaccuracy in the fixedbase and linear ssi assumptions when compared to its nonlinear flexiblebase counterpart. moreover, it is also found that disregarding the foundation flexibility effect may lead to over prediction of the interstory drift, force and ductility demands of the lowrise steel structure.