| Summary: | 碩士 === 朝陽科技大學 === 營建工程系碩士班 === 92 === This dissertation is a study for using the simulated transfer function obtained from the impact-echo method to evaluate the material properties of substrate layer for a laminate concrete structure. The peak amplitude in impact-echo spectrum may be varied by the energy and the contact time produced by the impact force. The experimental result needs to be transformed into transfer function for quantitative evaluation. The different acoustic impedance (Z) in substrate layer such as air, earth or water may lead to different spectral amplitude corresponding to concrete layer. Thus it is possible to non-destructively evaluate the substrate geological state for tunnel, mining pit or dike which is unfit for coring. The purpose of this study is as following.
1. Explore the connection between the experimental spectral amplitude corresponding to the interface of a composite concrete plate in transfer function and acoustic impedances for different substrate layers such as epoxy, gypsum and low-strength concrete.
2. Using numerical simulation to study the relationship between ratio of acoustic impedance for substrate and concrete layer (Z2/Z1) and the spectral amplitude corresponding to the interface in transfer function. The thickness of substrate layer is also concerned as a variable.
The experimental results show, for various tests applying on the same specimen, the spectral amplitude corresponding to depth of the interface may differ greatly. After transformation, the amplitudes in the transfer functions become stable. Take the experimental parameters into the previously developed equation for relating peak-amplitude to the thickness of a pure concrete plate without substrate layer. The predicted amplitude for the 10 cm-thick plate is 1.571, which has 11.5% error to the average experimental amplitude, 1.39. The relation between Z2/Z1 ratio and spectral amplitude corresponding to the interface in transfer function developed by numerical model can be used for predicting the experimental results for composite plates. Comparing the numerical and experimental results of composite plates with epoxy, gypsum, low strength mortar substrates, the order of spectral amplitudes values are epoxy >Gypsum > low strength mortar. The correlation is high.
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