報告書番号

N05

タイトル（和文）

常時微動計測に基づく大型構造物の振動特性評価技術 -稼働中の設備や工事によるノイズに埋もれた微小振動にも適用可能な高精度なシステム同定法の開発-

タイトル（英文）

Modal identification techniques of large civil-structures based on ambient vibration measurement -Novel system identification technique for ambient vibration contaminated with mechanical noises-

概要 （図表や脚注は「報告書全文」に掲載しております）

大型構造物の振動特性(固有振動数や減衰定数，固有モード)を常時微動計測から評価するための振動モード同定法と，その振動特性から層剛性を評価する手法を提案し，事務所ビルや発電所構築物などを対象とした応用例を示した。本研究で提案する常時微動計測に基づく振動特性評価には，次の利点がある。(1)低コストで振動特性の長期データが得られる。(2)その長期モニタリングデータに基づいて環境条件や供用条件に対する振動特性の依存性が分析できる。(3)常時微動記録のみからでも大規模構造物の振動特性が精度良く評価できる。(4)発電稼働中や補強工事中の建物のように，機械振動ノイズが常時微動に多く含まれる場合にも振動特性が精度良く評価できる。 (5)風や交通振動，機械振動などの振動源の特定が困難な場合にも，振動特性を評価できる。(6)構造的損傷が発生したときには，固有振動数や剛性の損傷前後の変化を明瞭に検出できる。

概要 （英文）

A novel modal identification technique based on ambient vibration test (AVT) for large civil-structures has been developed so as to estimate dynamic properties of, such as a natural frequency, a damping ratio and modal vectors. By using the technique, one can identify dynamic properties of a building with soil-structure interaction, where the mode shapes and damping ratios can be estimated accurately from a building record excited by wind forces as well as ground motion such in ambient vibration state. The following identification technique of story stiffness, which can be employed for checking structural design efficiency or structural construction validity in completion of a new building, and for detecting structural damage or aging effect in structural health monitoring, is also devised in the report.. In the report, the calculation schemes of the modal identifications and the stiffness identification are stressed as a powerful tool for estimating the dynamic property of an existing large structure, and four real large structures have been demonstrated on practical problems with modal identification; eg. A long-term vibration monitoring of the natural frequency of an office building, evaluation on stiffness retrofitting works, one-year evaluation on the dynamic property of a large arch dam affected by a reservoir water height, evaluation on the dynamic property of a tall stack in fuel power plant in the operating state, the damage detection test on a four story office building by using long-term vibration monitoring. Through these demonstrations, the dynamic property evaluation based on the ambient vibration measurement, presented here, has the following advantages: (1) Long transition of modal property is well-estimated at low cost. (2) Dependency of the modal property on the atmospheric or operation conditions can be easily obtained form the long transition data. (3) Only from ambient vibration record, the modal vectors of the large arch dam are well-estimated with minimum labor efforts. (4) Accurate estimation of modal property can be obtained even in the fuel power stack with generating electric power, or even in the retrofitting building under construction. (5) Shifts of natural frequency or story stiffness are clearly detected from their long-transitions at occurance of structural damage.

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