DISCUSSIONS ON VIBRATIONS CHARACTERISTICS OF BASE ISOLATED LOW RISE BUILDING BASED ON MICROTREMOR MEASUREMENTS AND FEM

摘要

This paper reports an attempt to infer some vibration characteristics (especially, predominant frequency) of base isolated buildings using microtremor measurements. A comparison between the vibration characteristics of this base isolated building and a similar RC 3-story building having direct foundation is performed. The inferred vibration characteristics from microtremor measurements for both buildings are compared with the predominant frequencies of transfer functions of accelerograms recorded at both buildings during the 2003 Miyagi-ken Oki Earthquake (M7.2). In general, the first normal mode of vibration is expected to be the predominant in base isolated buildings. However, the effect of the second normal mode detected slightly from microtremor records,was strong in transfer functions of accelerograms recorded in this building. The vibration characteristics of both buildings were confirmed also using FEM models. As conclusion, the application of microtremor measurements could be a useful tool for inferring some vibration modes of base isolated buildings too.