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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 17 Abstracts search results
April 1, 1997
Allen G. Davis
Two 16-story reinforced concrete apartment blocks founded on drilled shafts (CIP piles) were damaged in the 1994 Northridge earthquake. In order to assess the viability of the buildings for retrofit, it was considered necessary to evaluate the integrity of the existing concrete drilled shaft foundations, which were only partially reinforced. This paper describes the use of various nondestructive testing methods for the foundation evaluation, including ground penetrating radar, parallel seismic and impulse response tests. The selected test methods proved to be successfir!, and provided an economical approach while obtaiuing maximum informatron about the integrity and future performance of the hidden foundation.
Editors: Stephen Pessiki and Larry Olson / Sponsored by: ACI Committee 228
ACI Committee 228 has been active in the field experiences in the area of nondestructive testing of concrete. This volume contains 16 papers of which many were presented at the two most recent technical sessions organized by the committee. The first session was held during the ACI Spring Convention in 1993 in Vancouver, BC, Canada. The second session was held during the American Concrete Institute Fall Convention in 1995 in Montreal, Quebec, Canada.
Note: The individual papers are also available as .pdf downloads.. Please click on the following link to view the papers available, or call 248.848.3800 to order.
M. Ohtsu, M. Shigeishi,
T. Okamoto, and S. Yuyama
Acoustic emission (AE) has the potential to be an effective tool in evaluation of concrete structures under the action of loads causing cracking. In conventional testing, several AE parameters are investigated to elucidate microfracturing behavior in concrete. To identify internal cracks, the AE location technique is available, which is based on measuring arrival time differences. By employing multi-channel AE observations, the location of a crack responsible for an AE source can be determined. To obtain quantitative information on crack kinematics, the procedure is further studied and a technique for kinematic characteristics of internal cracks is developed. The AE source is mathematically represented by a moment tensor, by which the classification of cracks into tensile and shear cracks and the determination of crack directions can be made. To implement the procedure into a conventional AE system, software named SiGMA (Amplified Green’s function for moment tensor malysis) has been developed. The analysis is readily available on an AE waveform analyzer system consisting of a digital waveform-recorder and a microcomputer (controller). The procedure is applied to a uniaxial compression test of a plate specimen with a through-thickness slit and to a tensile test of a reinforced concrete rigid frame. The crack locations, the classification of crack types, and the determination of the directions of crack motion are in good agreement with experimental findings. The results show the procedure certainly provides a new technique for kinematic identification of internal cracks.
Michael E. Kalinski
An unidentified vehicle recently struck the bottom of a railroad overpass and damaged one of the concrete beams in the overpass. The damaged beam was taken intact to the University of Texas where the Spectral-Analysis- of-Surface-Waves (SASW) method was used to nondestructively delineate the damaged zones. SASW measurements performed on the beam revealed a significant velocity contrast between damaged and undamaged zones. These measurements were consistent with visual inspection of the beam and also indicated the presence of cracking that was not visibly detectable. In addition, SASW measurements taken while repairing the beam revealed how surface wave velocity measurements can be used to monitor improvements in the integrity of a beam after each repair step.
N. A. Cumming and 0. S. Ooi
A major structural repair and strengthening program was undertaken at a large grain shipping terminal on Canada’s northwest coast. The work was required to correct problems of excessive cracking and internal delamination in the silo walls. During the repair work, it was necessary to survey 42 silos to locate zones of delaminated or deteriorated concrete. This was done successfully using the impact-echo procedure. This paper describes the impact-echo survey and its findings. It further discusses correlation of test results to actual conditions encountered in the field.
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