Title: Development of Impact/Resonant Vibration Signature for Inspection of Concrete Structures
Author(s): H. Thronton and A. Alexander
Publication: Symposium Paper
Appears on pages(s): 665-680
Keywords: concrete durability; evaluation: nondestructive tests; piers; resonant frequency; safety; structures
Sinusoidal vibration and impact loading techniques have been tested in the laboratory and on field structures. An impact system has been tested which has proven more economical and versatile than the more commonly used sinusoidal system. With transient loading, a broad band of frequencies (including the resonant frequencies) is applied to the structure simultaneously rather than sweeping through each frequency one at a time. The resonant frequency of a structure is directly related to its dynamic Young's modulus and hence its mechanical integrity. Factors that influence the soundness and safety of a structure such as continuity and boundary conditions also directly affect the resonant frequency. With the availability of digital Fourier analyzers, mathematical functions such as spectra, coherence, and transfer relationships, permit the analysis of the behavior of large structures under dynamic con-ditions in-place and in real-time. Results of laboratory and field tests established the feasibil-ity of determining mechanical properties and assessing other factors that influence the soundness and safety of concrete structures using this nondestructive testing technique.