Performance of Elastomeric Seismic Isolators under Long-Period Earthquakes

Abstract

This research investigates the performance of elastomeric (laminated rubber) seismic isolators for the protection of medium-rise structures under the effect of long-period earthquakes. A finite element model of a midrise structure with elastomeric seismic isolators has been modeled and the dynamic performance of the structure has been examined under the effect of the 1985 Michoacan (Mexico City), 2003 Tokachi-Oki, 2010 El Mayor, and the 2016 Kaikoura earthquakes. The performance of the structure is studied in three cases, all equipped with elastomeric isolators with different natural periods. The natural-period of isolators in the first, second, and third cases is 2.5, 4, and 5 seconds, respectively. The comparison of the three cases in terms of mitigating earthquake energy shows that the effectiveness of elastomeric seismic isolators with lower periods (2-3 seconds) is significantly limited under the effect of long-period earthquakes. In common practice, elastomeric seismic isolators are produced and used with a natural period of 2-3 seconds, a seismic isolator having a period within the mentioned range will have serious shortcomings for dissipating earthquake energy when subjected to a long-period earthquake. The results of this study indicate that elastomeric seismic isolators with 5-seconds exhibited considerably better performance compared to that of 2.5 and 4-second seismic isolators.