Modal Identification and Damage Evaluation of Monorail Bridge Expansion Joints Using Multipoint Hammering and Reciprocity Theorem

Abstract

In straddle-type monorail, the expansion joints installed at boundary of the track girders can experience cracks and spalling in the cover concrete due to the train induced impact loads. The engineers conduct hammering inspections four times a year, requiring a huge amount of manpower. In this study, to automate the damage detection in hammering inspections of expansion joints, the modal characteristics are identified by multi-point hammering and reciprocity theorem, and the damage effects on the modal characteristics are investigated. As a result, the modal amplitude of the claws at damaged concrete increases around 1100 Hz. Utilizing this characteristic, a damage evaluation and a damage area estimation method based on hammering the four claws of the expansion joint plate are proposed.