Air-coupled ultrasonic system for fusion of impact-echo tests and surface wave measurements

Abstract

The main objective of this study is to develop a prototype air-coupled ultrasonic system (ACUS) for simultaneous data collection of impact-echo tests and surface wave measurements in concrete bridge decks. The ACUS includes two hexagonal air-coupled sensor arrays, each of which includes a solenoid-driven impact source at the center and six air-coupled sensors (ACSs) with parabolic acoustic reflectors (PARs) at vertices of a hexagon. The developed ACUS will be used as a part of an automated nondestructive evaluation and rehabilitation system (ANDERS) for concrete bridge deck inspection. First, a prototype hexagonal ACS array with PARs was developed in laboratory, and the prototype ACUS was built by combining the two hexagonal ACSs in a row. Second, an advanced data interpretation and visualization algorithm for the ACUS was developed for presenting the resulting data from individual test method, and data fusion of the two methods. Third, acoustic scanning was conducted using the developed ACUS over a simulated concrete bridge deck having various artificial defects (delaminations, surface-breaking cracks, segregated aggregates, partially grouted tendon ducts, and accelerated corrosion test regions). The results were visualized as several defect maps (i.e., frequency map and energy map from the IE testing, and velocity and transmission map from the surface wave measurements). In addition, the images from the two different test methods were combined by using a proposed fusion algorithm. It will be demonstrated that the ACUS is very effective for improving speed of data collection, and that the innovative fusion algorithm enables more accurate data interpretation.