Assessment of concrete structures using the Mira and Eyecon ultrasonic shear wave devices and the SAFT-C image reconstruction technique

In the mid-twentieth century, researches began developing digital technology. Digital format, simply stated, is the recording of information in a binary code of combinations of digits 0 and 1 [1]. Digital technology enables immense amounts of information to be compressed and stored [2]. The advent of digital technology has encouraged many innovations in the computer industry, medical field, science and engineering, and other scientific fields. One of the most fascinating innovations of the last century was the development of digital three-dimensional (3D) imaging; some of which include images of the human body (MRIs, CAT-scans) and 3D digital cinematography. Similarly, but at slower pace, manufacturers of nondestructive testing equipment have also began to develop 3D imaging technology. Commercially available equipment to perform ground-penetrating radar, scanning impact-echo, and ultrasonic pulse velocity are already integrated with powerful software algorithms to produce two-dimensional (2D) or three-dimensional (3D) display of the test results. This paper describes the basic features of the ultrasonic test equipment developed in the early 2000s, commercially known as Mira and Eyecon. These two instruments utilize a patented array of dry point contact (DPC) shear wave transducers to produce 2D and 3D tomographic images of the reflected waves. This new technology is allowing engineers to obtain in situ images of test results to understand the real time state of the structure under consideration. This paper also discusses an introduction to shear waves (S-waves), a brief description of the DPC transducers, the image reconstruction method, and synthetic aperture focusing technique (SAFT). Finally, several case studies involving laboratory and field applications on different kinds of structures and materials are presented. The conclusion section offers a summary of the main features and limitations of the Mira and Eyecon systems. (C) 2011 Elsevier Ltd. All rights reserved.