Influence of soil–structure interaction (structure-to-soil relative stiffness and mass ratio) on the fundamental period of buildings: experimental observation and analytical verification

Abstract

In order to investigate the influence of soil–structure interaction (SSI) on the dynamic characteristics of buildings, a series of free-vibration experiments were performed on a 1/4-scale steel-frame structure. The structural fixed-base fundamental period was for the first time determined by experiments as to avoid evaluation errors in the conventional SSI analyses, and its numerical counterpart obtained by using SAP2000® was also given for comparison. A total of 34 scenarios, which varied with regard to overall stiffness and mass of the structure, were examined in the experiments and the numerical simulations. In each experimental scenario, the fundamental period of the structure was determined under fixed-base and flexible-base conditions. A newly proposed method by Luco using Dunkerley’s formula to evaluate the lower bounds for structural natural frequencies considering SSI was validated by both experimental and numerical results. This method was found to exhibit excellent accuracy in predicting the fundamental period of the structure with SSI. This experimentally verified formula, having a broader application potential than the Jennings and Bielak and Veletsos and Meek expressions, could apply to a variety of researching areas in earthquake engineering and would be a useful reference for future seismic code revisions in assessing the basic period of the structure with SSI.