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Research Activities: 2004
Cyclic Load Testing and Acoustic Emission Methods of In-Situ Load Testing: Comparison and Development of Evaluation Criteria
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Matching Research Agency
University of South Carolina
One graduate student
For the past several decades in-situ evaluations have been carried out according to the 24-hour load test method and its associated evaluation criteria. It has become clear that the evaluation criteria for this method are not suitable for most present day RC buildings. Furthermore, conducting a 24-hour load test is time consuming in terms of performing the test.
There is a clear need for a more suitable method for evaluating existing reinforced concrete structural systems. This need arises in some cases due to a change in use, such as heavier loads being applied. In other cases this need arises from observed behavior that is cause for concern in regard to the safety of the structure. The goal of the proposed work is to further the development of a proposed load test method (the Cyclic Load Test method) through the addition of another proposed load test method (the Acoustic Emission method) that is sensitive to different types of damage. The work will be carried out in an organized and thoughtful manner and meaningful conclusions will be drawn.
The objective of the proposed research project is to compare the results of two recently introduced nondestructive load test methods to the existing 24-hour load test method described in Chapter 20 of ACI 318-05. The two new methods of nondestructive evaluation are the Cyclic Load Test (CLT) and Acoustic Emission (AE) methods. Each method offers advantages over the 24-hour load test method and each is particularly well suited to different aspects of structural evaluation. The focus of the research effort is an existing reinforced concrete (RC) building in Kansas City, Missouri. This building provides an ideal real world test bed for comparison between the three different methods of in-situ evaluation (24-hour, CLT, and AE methods).
Preliminary results from this experimental campaign will form the basis for future research related to the appropriateness of each method and the understanding of each method on a more fundamental basis. The research proposed will provide the initial data that is necessary for the successful pursuit of larger funds from international agencies. The proposed seed monies will be used as the basis for follow-up grants that will be written to the National Science Foundation, the European Community, the Engineering and Physical Sciences Research Council (EPSRC) and other agencies to test full-scale structures in the laboratory and in the field in order to validate the changes proposed by ACI 437: Strength Evaluation of Existing Concrete Buildings and to provide sufficient engineering evidence that is currently missing.
Benefits to ACI technical committee activities : The ACI technical committee that will most directly benefit from this research effort is ACI committee 437: Strength Evaluation of Existing Concrete Buildings. Drs. Ziehl and Casadei are active members of this committee and the results of the research investigation will be shared at all meetings until the conclusion of the project. Other committees that will benefit are ACI committee 228: Nondestructive Testing of Concrete and ACI committee 342: Evaluation of Concrete Bridges and Bridge Elements.
Benefits to the concrete industry: The concrete industry will directly benefit from this research work because the results of the research will be used to develop more meaningful in-situ evaluation methods for RC structures. Currently, the 24-hour load test method is being used to evaluate RC structures. Due to the limitations of this method and its evaluation criteria as described previously, this is not viewed as a meaningful or practical means of evaluation. The further development (i.e., more experimental data) of the proposed Cyclic Load Test method and the enhancement of this method with Acoustic Emission data and evaluation criteria will serve the purpose of providing a load test method that is both rapid and meaningful. The results of this research investigation will be the basis for requesting further funding to national as well as international agencies for conducting more research in this area. It is very important that further testing on real structures be performed to increase the database of load test case studies and that more fundamental knowledge of the methods and their evaluation criteria be gained.
Relationship to other Research/Projects
Technology Transfer Activities
The following are the technology transfer activities for the current investigation:
Transportation Research Board Keywords
Crack Propagation, Structural Assessment, Inspection and Mitigation Strategies, Risk Management, Cyclic Load Testing, 24-h Testing, Acoustic Emission