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Determination of In-Situ Stresses From Acoustic Emissions

by A. K. Maji,



Document Type: Proceeding Paper

Part of: Engineering Mechanics

Abstract:

Acoustic emissions (AE) are microseismic activities that are generated in concrete by cracking and damage. The rate of Acoustic Emissions, called the 'Event Rate', can provide indication of the amount of pre-loading that the material has been subjected to in the past. Upon repeated loading, AE events reappear only when the previously applied stresses are exceeded. This phenomenon called the 'Kaiser Effect' has been verified for different materials, as well as for concrete. However, its validity in concrete is a function of the type of loading, and the time in between subsequent loadings. Although many test methods are available to determine the in-situ strength of concrete, it is extremely difficult to determine in-situ stresses in various regions of a concrete structure. However, this information is important in assessing the adequacy of an existing structure. This paper investigates the possible use of the AE event rates to determine the level of stresses in plain concrete and reinforced concrete members. Remaining life and load carrying capacity of the structure can then be reassessed on the basis of the in-situ stresses and the in-situ strengths of the concrete. Acoustic emissions from reinforced concrete (RC) were monitored to evaluate the possibility of using the acoustic emission event rates and frequency characteristics for evaluating reinforced concrete members and structures. Tests were done on RC beams under flexural loading. Event rates were monitored on the beams, while the frequency characteristics were monitored for all the different types of test specimens.

Subject Headings: Field tests | Reinforced concrete | Acoustics | Emissions | Concrete beams | Load tests | Load factors

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