| Summary: | 碩士 === 國立臺灣大學 === 土木工程學研究所 === 105 === Concrete is one of the widely used construction material in infrastructures owing to its high durability, low cost and economic advantages. However, cracks tend to propagate under internal and external stresses in concrete, thus affecting its strength and durability. Surface cracks of concrete are the only indexes that can be observed with naked eyes and easily identified.
This study involves monitoring and quantifying surface cracks of concrete to conduct the connection between surface crack characteristics and mechanical properties of concrete under uniaxial compressive loading. Digital image measurements are applied in this research to measure the crack characteristics and to establish the relationship between axial strain, lateral strain, volumetric strain and axial stress. The crack characteristics include crack density, average crack length and maximum crack width, etc. With the data of uniaxial compression tests of concrete, regression analysis is also accomplished to obtain the correlation between concrete strength and crack characteristics. The experimental results show that the concrete subjected to uniaxial compression is affected by geometric properties and boundary conditions. Moreover, maximum crack width and the stress loss are linearly increasing, while crack density and the compressive fracture energy are logarithmically increasing. The regression results in this study can be further applied to estimate residual strength of concrete with certain crack characteristics.
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