Development of the EDR-Spring Element Using Foamed Polymer Materials and the Design of NSE-Isolated Buildings Using EDR-Spring Elements

Abstract

Seismic Isolation can provide superior building safety during strong earthquakes, but it is known that some near-source ground motions produce excessive response deformations, and these may be larger than the allowable capacity of the isolation devices. “Seismic Isolation with No Strain Energy” (NSE), a new isolation concept, has been proposed as a solution to the problem. By eliminating the strain energy stored in deformed isolators, the resulting resonance problem can be completely resolved. The goal of the paper is to successfully produce an NSE spring element which has the restoring characteristics of the EDR-spring model for NSE-isolated buildings. The paper tested 15 foamed polymer materials and selected the most suitable one for the EDR-spring element. It has an elimination ratio of stored strain energy of ß≥0.7. The design loop for the spring using the selected material was established, and two model buildings of 5 stories and 15 stories were designed using the EDR-spring and sliders supporting the buildings’ weight. The designed NSE-isolated buildings’ superior dynamic performance against very strong earthquakes, even in cases in which input ground motions have the same predominant period as the isolated structures, was confirmed by dynamic response analyses.