Standard Article

System Identification for Soil—Structure Interaction

Civil Engineering Applications

  1. Erdal Safak

Published Online: 15 SEP 2009

DOI: 10.1002/9780470061626.shm178

Encyclopedia of Structural Health Monitoring

Encyclopedia of Structural Health Monitoring

How to Cite

Safak, E. 2009. System Identification for Soil—Structure Interaction. Encyclopedia of Structural Health Monitoring. .

Author Information

  1. Kandilli Observatory and Earthquake Research Institute, Bogazici University, Department of Earthquake Engineering, Istanbul, Turkey

Publication History

  1. Published Online: 15 SEP 2009

Abstract

The term soil–structure interaction (SSI) refers to the influence of the deformations of the ground on the dynamic response of a structure. It is an important phenomenon of seismic excitations. If a structure is founded on rock, it is reasonable to assume that the ground does not deform and the structure is rigidly fixed at the base. If it is founded on soil, however, the flexibility of soil will cause the foundation of the structure to have translational and rotational motions when it is vibrating. SSI can significantly alter the vibration characteristics of a building and, consequently, the characteristics of recorded motions from that building.

The dominant frequency recorded in a structure with SSI is always smaller than that without SSI. When the foundation motion is taken as the input, a structure with SSI is a noncausal system because of the coupling between the motions of the foundation and the superstructure. For building-type structures, the presence of SSI can be detected by comparing the dominant frequency of the top floor motions with the dominant frequency of the foundation-to-top floor transfer function. The dominant frequency of the top floor motions corresponds to the frequency with SSI, whereas the dominant frequency of the foundation-to-top floor transfer function corresponds to the frequency if the building were fixed-based. If these two frequencies are equal, there is no SSI. The presence of SSI can also be detected by investigating the causality of the building's foundation-to-roof impulse response function. For causal systems, the amplitudes of the impulse response function at negative times are zero, whereas for noncausal systems they are comparable with those at positive times.

Keywords:

  • soil–structure interaction;
  • system identification;
  • dynamic response;
  • structural response