| Summary: | 博士 === 國立成功大學 === 建築學系碩博士班 === 94 === Chuan-Dou timber structures can be frequently found in historic buildings in Taiwan. Unfortunately, many Chuan-Dou timber structures were destroyed during the Chi-Chi earthquake of 1999. Since then, the seismic behavior of these traditional timber structures has attracted much attention. Joints are one of the most important factors that affect the global structural behavior of timber structures due to its semi-rigidity. The structural behavior of timber joints have been touched from time to time, but not further studied. This dissertation attempts to explore the rotational performance of these timber joints of Chuan-Dou timber frames.
The field survey indicated that the traditional timber joints involve three various types, including continuous, flat cut and dovetail connected joints. Methodology to clarify the joint type nondestructively was firstly proposed in this dissertation. The method takes stress wave velocity and amplitude transmission ratio into account to classify the joint type without dismantling. A total of 72 specimens were tested to study the various types of timber joints. The mechanical failures, bending-slip characteristics, initial rotational stiffness and the relations of timber joints were discussed. Models to predict the initial rotational stiffness and curves of each type joints were proposed. Once we can classify the joint type by using the nondestructive method proposed previously, we can estimate the initial rotational stiffness and curve of a timber joint. Comparisons were made to discuss the effect of discontinuing the beams and effect of dovetail connection. It can be found that discontinuing the beam will significantly degrade the rotational performance of a timber joint. Although connecting the individual beams by using dovetail mechanism can help to improve the structural behaviors of timber joints, it is only suitable in the case that column widths of joints are less than 18cm. Termite attack is the major bio-degradation to timber structures in Taiwan, due to humid and hot environment. A model to consider the performance degradation of timber joints induced by termite was proposed by experiments on specimens with simulation of the termite attack. The results show that the beams of timber joints are sensitive to termite attack.
The results of this dissertation can not only being applied in evaluation of rotational performance of existing timber joints, but also help to estimating the structural behavior of newly designed timber joints.
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