Assessment of Historic Concrete and Masonry by Broadband Vibration Testing

Abstract : The assessment of historic concrete and masonry requires a number of diagnostic tests that involve a low-energy impact of the structure and the acquisition and processing of the resulting vibration signals from the structure. This project involved the determination of methods suitable for automation and combination, and the prototyping of these methods in a pair of historic buildings on a DOD installation. The objectives of the project were to test the merit of structural investigations using the air-coupled impact-echo method, which relies on microphones rather than contact devices to obtain diagnostic information, and to determine the suitability of this method for automation and integration with the experimental modal analysis method. The project also included the development of a prototype automated impactor using compressed air-driven hardened steel balls of various diameters. It was found that the air-coupled method was effective in discriminating flaws in masonry and concrete. It was further found that this method can be developed into an automated scanning method for horizontal and vertical surfaces.