Influence of asphalt on fatigue crack monitoring in steel bridge decks using guided waves

Asphalt materials generally exhibit temperature-dependent properties, which can influence the performance of fatigue crack inspection and monitoring systems for bridge deck structures. For a non-intrusive fatigue crack sizing methodology applied to steel decks using ultrasonic guided waves, the effect of asphalt has been investigated. A higher-order spectral finite element model has been implemented to capture the propagation characteristics of guided waves in the multi-layer waveguide. Experimental evaluation has been performed on an aluminum plate covered with bitumen. The results reveal that the extent of the effect of asphalt on propagation of guided waves depends on the type and layout of the asphalt. For a particular asphalt type of interest, i.e. open asphalt surfacing, however, this effect appeared to have limited influence on the performance of the crack sizing methodology, i.e. in the order of a few percents. In the analysis, temperature variation, and uncertainties in the material properties and asphalt bonding condition have been taken into account.