河川橋梁橋脚の健全度に関する状態監視手法

摘要

The soundness of the structural stability of railway bridge piers across a river deteriorates over time because the riverbed and overburden that support the piers can be gradually eroded by river flows. An inspection of the soundness is carried out by measuring the natural frequency of a primary mode derived from the free vibration of the piers generated when an impact force is applied to them through a field test. On the other hand, it is expected that along term monitoring method improves efficiency in the inspection compared with the field test. In this study, soundness indices for the long-term monitoring with the area ratio of the acceleration power spectrum of microtremors and the ratio of the amplitude of acceleration during train passage were proposed through experimental model tests and in situ measurements. Consequently, it was confirmed that there was a correlation between the indices and the natural frequencies of piers. In addition, the soundness evaluation of the piers was performed by the indices obtained from the long term monitoring.%河川橋梁では,河床低下や洗掘の影響により,橋脚の安定性に関する健全度の低下が生じる。現状,この健全度の評価は,河川の潯筋の変化等を目視確認する定性的な評価や衝撃振動試験から得られる橋軸直角方向の固有振動数で評価されているが,橋脚に常設した計測器で健全度を状態監視する手法により,検査の効率化による維持管理コストの低下が期待できる。そこで本研究では,橋脚の健全度評価のための状態監視手法の構築を目的として,橋脚の固有振動数と相関を有する健全度診断指標を新たに提案し,橋脚に常設した加速度計で長期計測したデータから橋脚の健全度を評価する手法を提案した。また,計測データを無線伝送するシステムを開発し,河川橋梁橋脚の健全度に関する状態監視手法を提案した。