Computing the modal characteristics of structures considering soil-structure interaction effects

Abstract

Modal analysis of structures is usually performed based on finite element models where the structures are considered undamped and fixed at their base, disregarding any interaction with the soil. In some cases though, these modeling assumptions may lead to erroneous estimates. This paper presents a finite element-perfectly matched layers model which is used to compute the modal characteristics of a frame structure considering dynamic soil-structure interaction effects. The modal characteristics of the structure are computed with respect to the soil stiffness revealing the key effects of dynamic soil-structure interaction. The analysis shows how soil-structure interaction affects the fundamental as well higher modes of the structure, involving increase in modal damping ratios and engendering complex valued mode shapes.