伝統木造五重塔の動的挙動の調査
常時微動と自由振動の測定

設計解析により耐震および耐風安全性を確認した木造伝統構法五重塔の竣工時に、常時微動と人力加振による自由振動実験を行い、固有周期、振動モード、減衰定数、振動軌跡、変形比等の基本的な動特性を求め、設計解析や既往の実測研究と比較した。本調査では、塔身とともに、心柱の固有周期や減衰定数も求めた。塔身の常時微動と自由振動実験による固有周期や振動形、振動軌跡、変形比は、既往の木造五重塔の微動実測の結果とおおむね対応したが、設計解析の固有周期や振動形とは合致しなかった。設計解析の妥当性をより正しく評価するためには、今後、大変形を伴う地震や台風時の観測が望まれる。

Dynamic Characteristics of Newly-Built Traditional Five-Storied Timber Pagoda
Measurement of Microtremor and Free Vibration

Microtremor measurements and free vibration tests of the newly-built traditional timber five-storied pagoda were carried out to investigate its dynamic characteristics. The recorded natural period, natural modes and displacement ratio were compared with those of its structural design analysis model and the past experimental studies. Although the measurements were consistent with the past studies of the historical timber pagodas, there showed a significant discrepancy between the measurements and the analysis model. In order to verify the structural analysis model precisely, earthquake and typhoon observation at the pagoda will be need to record dynamic behaviors at the high-level response.