| The objective of this study was to assess the applicability of stress wave technique as a quick and effective means to determine the mechanical properties of structural timbers in ancient architectures without damaging the original materials or altering the structures. The project was mainly focused on nondestructive evaluation of Larch (Larix principis-rupprechtii Mayr.) timbers, a typical softwood species used in the construction of ancient timber structures in China. The wood specimens used for the study were cut from both new timbers and the old structural members removed from an ancient architecture. Laboratory experiments were conducted to obtain stress wave speed, moisture content, bending stiffness and strength in, as well as compression strength of the specimens. Analysis was then performed to use stress wave speed as a NDE parameter to predict the mechanical properties of the wood.The laboratory results indicated that the stress wave speed had linear relationships with the modulus of elasticity. modulus of rupture, and the compression strength. The correlation coefficients of the regressions were0.54.0.36. and0.38respectively. Subsequent tests of the full size wood beams demonstrated that stress wave method can be used to test in-service structural timbers for determination of mechanical properties.To further improve the accuracy of property prediction for ancient architectural timbers, we combined stress wave speed with a micro-drilling resistance measure in the prediction models. Considering the variability of the regression models, the lower5%exclusion line of the regression equations were suggested for evaluating the residual mechanical properties of structural timbers in field applications.The methodology and evaluation procedure developed in this thesis has been applied to two ancient architecture inspection cases:the Granary at Xian Nongtan, and the Animals Slaughtered Pavilion at the Temple of Heaven in Beijing. |
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