Monitoring for fatigue crack geometry in orthotropic steel bridge decks by application of reflected Lamb waves

• Published in: Thin-walled structures 2023-11, Vol.192, p.111170, Article 111170
• Main Authors: Shi, Linze, Cheng, Bin, Xiang, Sheng, Li, Derui, Liu, Tiancheng
• Format: Article
• Language: English
• Subjects: Fatigue cracks; Geometry monitoring; Optimal sensor arrangements; Orthotropic steel bridge decks; Reflected Lamb waves
• ISSN: 0263-8231; 1879-3223
• DOI: 10.1016/j.tws.2023.111170

•Experimental and numerical investigations were conducted to examine the impact of reflected Lamb waves on fatigue crack monitoring.•The variations of standardized wave features from reflected waves with the increase of fatigue life and the variation of crack geometry were investigated.•The effect mechanism of crack geometry to standardized wave features was revealed based on the experimental and numerical results.•The optimal arrangements of wave sensors for crack monitoring at deck-to-rib connections and rib-to-floorbeam connections were determined. Orthotropic steel bridge decks (OSDs) have been widely used as a crucial load-bearing structures in long-span bridges,. However, the weld connections in OSDs are susceptible to fatigue crack initiation due to the high stress cycle caused by vehicle loads. Reflected Lamb waves have potential in the monitoring of crack geometry, and different sensor arrangements are employed for different crack types in OSDs. Three full-scale specimens were fabricated and tested with the recommended sensor arrangements to continuously monitor two types of cracks in tests. Finite element models were also established and verified by the experimental results. Parametric studies were conducted to investigate the effects of sensor arrangements, crack lengths and angles on monitoring results. A wavelet transform algorithm was applied to analyze reflected waves and extract standardized wave features, based on which the crack geometry was evaluated. The experimental results reveal that the standardized wave features from the reflected Lamb waves change significantly with the increase of fatigue life, indicating that the features are sensitive to fatigue crack growth. The simulation results reveal that the standardized wave features effected by crack geometry are positively correlated with projected crack lengths perpendicular to the direction of wave propagation. The optimal arrangements of wave sensors for crack monitoring at deck-to-rib connections are to place excitation and reception sensors at 200 mm and 60 mm from the welds at crack initiation plates, respectively; while for cracks at rib-to-floorbeam connections, excitation and reception sensors are located at 200 mm and 50 mm distant from the horizontal welds at cut-out, respectively, and all sensors are 50 mm distant from vertical welds.