The text outlines several challenges and limitations associated with using ultrasonic guided waves for non-destructive testing (NDT) on a bridge structure. Here are the main points:

Challenge 1: Environmental variations

• Rain can cause irregular environmental variations, leading to false alarms.
• Accurate detection of environmental variations is crucial to minimize false alarms.

Challenge 2: Damage localization

• The public benchmark dataset contains multiple guided wave reflections from the edge of the monitored structure, making it challenging to isolate damage-induced signals.
• Isolating damage-induced signals is challenging due to the long excitation signal duration and short distance between receivers on the plate.

Challenge 3: Detection and quantification of damage

• The size and shape of dents (damage) can affect the guided waves, making detection and quantification challenging.
• The severity of damage can result in different degrees of decline in optimal correlation coefficients.

Challenge 4: Damage type classification

• Damage types (e.g., through-hole damage) have varying effects on guided wave signals, requiring separate consideration for accurate detection.

Challenge 5: Real-world applications and uncertainty

• The public benchmark dataset is intended for theoretical evaluation of NDT methods, but its application in real-world scenarios may be limited by the challenges outlined above.
• There is a need to conduct further investigation to overcome these limitations and improve the accuracy and reliability of ultrasonic guided wave-based NDT methods.