アラカワ トシハル   Arakawa Toshiharu
  荒川 利治
   所属   明治大学  理工学部
   職種   専任教授
言語種別 英語
発行・発表の年月 2009/11
形態種別 国際会議議事録
標題 The Evaluation of Natural Frequencies and Damping Ratios of a High Rise Steel Building Based on Vibration Measurement
執筆形態 共著(筆頭者)
掲載誌名 Proceedings of Asia-Pacific Vibration Conference
巻・号・頁 13,pp.1-9
著者・共著者 *Arakawa Toshiharu,Hiroyuki KAMIO and Shigekazu YAMAMOTO
概要 Microtremors of a high rise building have been measuring in regularly once in two months until now since January 1999 and vibration characteristics are periodically observed as the structural monitoring. The building that belongs to Meiji University in Tokyo was completed in October 1998. This building of a moment resisting steel frame with seismic control walls made of ultra mild steel has rectangular plan and 120m height. Microtremors in two horizontal directions and torsional direction are measured in the midnight and many data have been collected. This study evaluates natural frequencies and damping ratios from 1st mode to 4th mode in each direction given by microtremor data. And the changes with passage of time for these vibration characteristics are examined on 120 months over. The 1st modal damping ratios are evaluated from 0.3% to 0.8% in horizontal directions and dispersion in each measurement time or day. The changes with passage of time for the natural frequencies are gradually decreased. The decreases of those at each direction or in lower modes are about 5.0% in ten years. Next, relations in the damping ratios of lower modes are also analyzed in each direction. It is estimated Rayleigh damping type at longitudinal direction and torsional direction, and proportional to natural frequencies that is stiffness proportion type at span direction. Last, relations between amplitude and 1st modal damping ratios in free vibration waves by Manpower Excitation are explained. It is clarified that the 1st modal damping characteristics depend on the amplitudes at lower vibration.