Identification of soil-structure interaction as the primary source of traffic-induced vibrations in a low-rise building: A nonlinear-elastic perspective

Abstract

Soil-Structure Interaction (SSI) effects may become significant for buildings situated on soft soil when coupled with specific foundation and superstructure flexibility characteristics. Under service conditions, traffic-induced waves can cause vibrations perceptible to building occupants, even when the structure fully complies with a conventional strength-based building standard. This investigation was based on records of a six-story building. Soil foundation was modeled through a semi-infinite elastic media representation. A calibrated model achieved estimations within an 8 % difference from actual field records. The results demonstrate that SSI induces a reduction of up to 40 % in the system’s lateral stiffness during its service state at overall drift ratios of about 0.0002 %. In contrast to research approaches focused primarily on inelastic behavior for seismic applications, this study presents a methodology to identify the presence of SSI, by tracking the frequency of an equivalent nonlinear-elastic model. This variation occurs as base movement activates foundation flexibility, leading to the coexistence of two distinct fundamental frequencies. The identification is achieved through a 2-DOF representation and it involves (a) analyzing the frequency content of ambient vibrations recorded with high-sensitivity instrumentation; (b) tracking the fundamental frequency as a function of displacement; (c) establishing a linear transfer function (TF) to isolate the effects of soil flexibility; and (d) comparing estimated forces applied at each DOF to localize the source of energy input. The method was successfully implemented to characterize the most probable scenario causing user-perceived vibrations. Despite its efficacy, the applicability of this approach may be limited in cases with low signal-to-noise ratios or highly rigid superstructures that preclude the coexistence of the fixed-base and SSI-influenced frequencies.