Seismic Response of SDF Equipment‐Structure, System

Abstract

A mode synthesis method is developed for obtaining the modal properties of a combined single‐degree‐of‐freedom (SDF) equipment and structure system in terms of the modal properties of the individual systems. The eigenvalues of the combined system are obtained as the roots of a simple non‐linear characteristic equation. A simple Newton‐Raphson solution technique can be used to solve this equation. Also, the closed form expressions are provided to calculate the eigenvectors. These combined eigenproperties can be utilized to calculate the structure or equipment response, such as floor response spectra, which will incorporate the effect of the dynamic interaction between the two systems. As no assumption is made about the size of the equipment in the development presented here, this approach can be used equally effectively with light as well as heavy equipment.