Evaluation of Reinforced Concrete Beam Specimens with Acoustic Emission and Cyclic Load Test Methods by ProQuest


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									 ACI STRUCTURAL JOURNAL                                                                                   TECHNICAL PAPER
Title no. 106-S28

Evaluation of Reinforced Concrete Beam Specimens
with Acoustic Emission and Cyclic Load Test Methods
by Zhiwei Liu and Paul H. Ziehl

This paper presents the results of the cyclic load test and acoustic                       RESEARCH SIGNIFICANCE
emission methods of evaluation applied to 14 reduced-scale                    There is a clear need for evaluating the structural performance
reinforced concrete beam specimens that represent different cases           of many reinforced concrete (RC) buildings and bridges.
in terms of failure mode (flexure and shear), loading pattern,
                                                                            Due to the relative newness of the CLT method, there is a
concrete mixture design, and resulting material properties. Five
acoustic emission evaluation methods are investigated to                    lack of historical data for validation of the acceptance
determine their ability to assess the damage level in the reinforced        criteria, especially with consideration to different failure
concrete specimens. Recommendations are provided related to the             modes (flexure and shear) and different concrete material
suitability of the evaluation criteria for the cyclic load test and         types. A similar case can be made for AE evaluation criteria.
acoustic emission methods.                                                  Of importance is that using both the CLT and AE evaluation
                                                                            criteria in combination may serve to increase confidence in
Keywords: acoustic emission; cyclic load test; nondestructive evaluation;   the evaluation results with little additional cost.
reinforced concrete.
                                                                                           BACKGROUND RESEARCH
                       INTRODUCTION                                            Mettemeyer and Nanni6 in 1999 proposed guidelines for
   Recent information indicates that more than 27% of bridges
                                                                            rapid load testing of RC structural members. This method is
in the U.S. are either structurally or functionally deficient.1
                                                                            referred to as the cyclic load test in Appendix A of ACI
Similarly, buildings are reaching their design life; and in many
                                                                            437R-03.3 Three evaluation criteria were established for this
cases, the ability to reliably calculate the ultimate capacity of
                                                                            method: repeatability, permanency, and deviation from
certain systems is complicated by the degree of end restraint,
                                                                            linearity. Later, Casadei et al.7 applied the CLT method to
variation in material properties, and other factors. In the case
                                                                            the evaluation of RC slabs of a parking garage and made a
of bridge structures, safely maximizing load ratings and
                                                                            comparison with the 24-hour test method. Test results
extending service life can save billions of dollars that would
                                                                            indicated that both the CLT method and the 24-hour LT
be needed for replacement. There is a critical need to develop
                                                                            yielded the same outcome (in that case, both methods led
an effective in-place evaluation loading procedure and
                                                                            to failure of the acceptance criteria under the same test
corresponding evaluation criteria to assess damage level and
                                                                            load). Recently, Ridge and Ziehl8 used the CLT method to
existing load capacity. Often there is no one method that can
                                                                            evaluate RC flexural specimens strengthened with carbon
provide the entire solution2; therefore, it may be preferable to
                                                                            fiber-reinforced polymer (CFRP) strips and made a
use a combination of methods.
                                                                            comparison with the AE method. The general conclusion
   The cyclic load test (CLT), as described in Appendix A of                was that both the CLT and AE methods provided an effective
ACI 437R-03,3 is a relatively recent load-test method. It not               means of damage detection; however, in one case, the AE
only reduces the testing time compared with the standard                    method provided increased sensitivity.
24-hour load test (24-h LT) method described in Chapter 20
of ACI 318-054 but may also provide improved insight into                      In regard to the AE method, many investigators have
structural behavior. Acoustic emission (AE) is another                      attempted to use AE parameters to quantify the damage level
in-place evaluation method that is well suited to assessing                 of RC structures. At least five such methods have been
damage levels of various types of structures while being                    reported. One important damage assessment method is the
loaded. AE is defined as “the class of phenomena whereby       
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