STUDY ON DEFLECTION MEASUREMENT OF SIMPLY SUPPORTED GIRDER BRIDGES BASED ON LASER-POSITION SENSITIVE DETECTORS
Deflection monitoring is an important part of bridge health monitoring.A high-precision deflection measurement system based on laser-PSD(Position Sensitive Detectors)for simply supported girder bridges is proposed.The system adopts a laser reflection method to amplify the deflection of simply supported girder bridges and realize static and dynamic monitoring of bridge deflection with micrometer-level accuracy.The composition and working principle of the system are firstly introduced,which can amplify the bridge mid-span deflection by more than 7 times through the laser reflection principle to achieve high-precision deflection measurement;Through theoretical derivation and error analysis,the influence of the placement of the laser transceiver and reflector on the deflection amplification factor is discussed;The effectiveness of the system is verified through experiments.The system can accurately measure the mid-span deflection of a simply supported girder bridge with an accuracy above 1µm for the measurement range of millimeter level.It can perform dynamic deflection measurements so as to identify dynamic parameters such as the fundamental periods of the bridges.The laser-PSD measurement system proposed in this paper features high accuracy,fast response,low price,and easy-to-implement for long-term dynamic monitoring.This study is expected to provide a reference for deflection health monitoring of small and medium span simply supported girder bridges.
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