Experimental study of secondary systems in base-isolated structure

This work investigates the response of secondary systems attached to a base-isolated, six-story model structure that is subjected to base motions. The secondary systems are modeled by cantilevered, inverted pendulums. They have natural frequencies and mass ratios that span a wide range of values. The scaled model structure is base-isolated through the use of sliding Teflon disc bearings coupled with restoring helical springs. The structural system is placed on a seismic simulator and is subjected to several prerecorded earthquake accelerograms. Time histories and frequency spectra for the secondary systems and their supporting floors are presented. Subsequently, a numerical model is developed to reproduce the results obtained from the experiments. The level of agreement between numerical and experimental results indicates that the numerical model can be used for the construction of floor response spectra (FRS) for the secondary systems. The experimental results and the numerical studies show that under most circumstances, this novel structural base isolation system reduces the effects of vibrations in the secondary systems.