NDE application of air-coupled ultrasonic array system and f-k domain analysis for delamination-like defect detection in bridge deck

Recent development of the air-coupled sensing technique provides great potential for practical data measurement in the field; however, an improved data analysis method and careful design of test configuration are required to inspect structures appropriately. Impact-echo (IE) is an efficient method to evaluate delamination-like defects in concrete bridge decks. However, practical application of air-coupled IE is limited due to direct impact and ambient noises. Another practical problem is the difficultly in data interpretation associated with the dominant flexural mode frequency. Although IE analysis is able to estimate a depth of delamination-like defect from the thickness mode frequency, it is well known that the flexural mode frequency is dominant for shallow delaminations but cannot provide the depth information. The structural inspection needs of many data and conventional IE schemes possibly mislead data interpretation. New concepts for IE data measurement and analysis are needed to evaluate full-scale infrastructure in the field.