Abstract：The orthotropic steel bridge deck (OSBD) is widely used in long-span bridges. However, fatigue cracks easily occur in OSBDs, which seriously affects the safety of bridges. Conventional nondestructive testing methods usually only cover the local region below the transducer, so there is an urgent need to develop structural health monitoring (SHM) technologies to scan a large area from a single position on the bridge deck. Compared with the dispersive Lamb waves, the fundamental shear horizontal wave (SH0 wave) is an ideal wave mode in developing SHM systems for OSBDs due to its non-dispersive characteristics, but the related research is extremely scarce. This paper first studies the interaction between an SH0 wave and a U-shaped stiffener with a weld by finite element simulations. It is found that below the first cutoff frequency of SH guided wave, the U-shaped stiffener and weld have little influence on the propagation of the SH0 wave in the deck plate and can be neglected. Above the first cutoff frequency, a part of the SH0 wave will be converted into the SH1 wave (the first-order SH mode) when encountering the U-shaped stiffener, but the amplitude of the generated SH1 wave is quite small. Then, piezoelectric transducers are developed for excitation and reception of single mode SH0 wave in a 16 mm-thick deck plate. The developed transducer for generating the SH0 wave is a thickness-shear piezoelectric device, while the sensor for receiving the SH0 wave is a face-shear piezoelectric transducer. After that, experiments are conducted to verify the simulated results for the case of an SH0 wave encountering the U-shaped stiffener. The obtained experimental results accord well with the simulated ones. Finally, an SH0 wave-based inspection system is developed to detect cracks in OSBDs. Results show that the cracks in OSBDs can be accurately identified by SH0 wave. This work can lay a foundation for developing guided-wave-based intelligent monitoring technology for OSBDs.
2023, Vol. 44 
