Dr. Jinying Zhu
Dr. Jiong Hu
Date of this Version
Nonlinear resonance techniques have been shown to be sensitive to microcracking in materials, including alkali-silica reaction (ASR) damage in concrete. However, application of nonlinear resonance tests have been limited due to the difficulty of application to large-scale field structures and the inability to quantitatively relate material nonlinearity with damage development. In this study, the development of ASR in concrete prisms and large concrete beam specimens of varying aggregate types and specimen sizes was monitored using linear and nonlinear resonance techniques.
For the concrete prisms, although the linear resonance frequency test could detect initiation and development of ASR damage in specimens with the reactive coarse aggregate, it failed in the specimens with the reactive fine aggregate. As a comparison, the nonlinear resonance test results not only detected the initiation of ASR damage for specimens of both reactive aggregate types, but also showed a strong correlation with ASR damage progression.
A nonlinear impact-echo (IE) method was proposed for concrete damage evaluation on large structures. The nonlinear IE method is similar to the nonlinear resonance test, but it excites the local thickness resonance mode. The method was validated on various beam specimens and the results demonstrate that the nonlinear IE method is more sensitive than the linear IE test and can be used for damage evaluation of large-scale concrete structures. The nonlinear results from the prisms and beam specimens were used to form quantitative relationships between expansion and material nonlinearity that can be used to assess ASR damage without a baseline (initial) measurement.
Advisors: Jinying Zhu and Jiong Hu