Condition assessment of bridge deck truss using in-service monitoring data of strain

In this study, an approach for structural condition assessment of bridge deck truss making use of in-service monitoring data of strain acquired from a SHM system is proposed and applied to the instrumented Tsing Ma Bridge. The proposed method is composed of structural assessment at two levels: (i) deck truss components, and (ii) cross-sections of deck truss. Since the in-service monitoring data of strain is a result of multi-source combinations due to live loads and environmental effect, wavelet-based multi-resolution analysis is first carried out to decompose the measured strain data sequences for signal extraction as some ingredient induced by temperature is released through boundary conditions and contributes little to stress quantities. Thereafter, the time-history of stress response in deck truss components due to live load effect is derived from the extracted strain and the peak values of resultant stress are counted to infer their statistical characteristics for component-level assessment. As for the cross section-level assessment, the dynamic internal forces on cross section are evaluated by synthesizing the internal forces of truss members. Subsequently structural condition assessment of deck truss section is carried out for varíous loading conditions such as monsoon, typhoon, with and without railway traffic.