Acoustic emission (AE) behavior, due to localized cracking and damage, was studied in 200 reinforced concrete beams, 65 in. x 6 in. x 1 0 in., under monotonically increasing three point loading conditions. The material variables that have been emphasized, consist of: various concrete curing times (ages), amounts of tension and compression steel reinforcement, and significant glass fiber additions to the concrete mix. A total of 420 cylinders (6 in. x 12 in.) were tested to ascertain the range of material strength was minimal. Varying compression steel and tension steel areas, induced variations in the gross failures (observed cracking and/or load decrease) although diagonal tension failure predominated. To date, comparisons have been established that substantiate direct correlations between the degree and type of reinforcing and the subsequent AE parameters of energy rate, events, counts and hits. It is these AE parameters that will decrease at defined rates as curing time increases. Results show that AE indicators give rise to a substantially increased level of activity at the steel yielding point, as well as at catastrophic beam failure. For a given reinforcement condition, distributions of almost all examined parameters, especially energy, events and rise time were found to be almost identical in all tested concrete beams. The peak energy rate and event level, with its corresponding duration interval will describe the physical condition of a concrete beam at different loading stages and reinforcement conditions. It was further determined that AE does not provide early warning of incipient structural problems for the tested concrete beams. This differs from behavior observed in steel and aerospace composite materials.
Jenkins, David R.
Master of Science (M.S.)
College of Engineering
Civil and Environmental Engineering
Structures and Foundations
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Masters Thesis (Open Access)
Dissertations, Academic -- Engineering; Engineering -- Dissertations, Academic
Steputat, Christian C., "Acoustic emission spectra of steel and fiber reinforced concrete beam specimens as induced by static loading" (1993). Retrospective Theses and Dissertations. 3744.