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The mechanical property of timber is a prerequisite for the evaluation of ancient timber structures. The main mechanical properties of three kinds of timber including the old Tibetan Populus cathayana, new Tibetan Populus cathayana and new Tibetan Pine were obtained by tests in this paper. The principles and assumptions made in the determination of these strengths and the time-dependent laws on the design strength of timber in ancient Tibetan structures were discussed. It is found that the physical and mechanical properties of Tibetan Populus cathayana have degraded greatly after hundreds of years. The strength degradation of a structural component can be attributed to the decay and cracking of timber when the stress ratio is low while it can be attributed to the creep of timber caused by the load duration effect when the stress ratio is high. The new Tibetan Pine is also checked to be a good material for the restoration of ancient Tibetan building due to its higher strength compared to the old Populus timber. [ABSTRACT FROM AUTHOR]

Tibetan ancient timber structure has great historical, cultural, artistic, and scientific values. The structural configuration of members such as wall, roof, slab, and timber skeleton with semirigid joints is studied in this paper based on field survey results. The aseismic characteristics of Tibetan ancient timber structure have been summarized and introduced. One of the unique features of the Tibetan ancient timber structure is its special beam-column joint which has a semirigid behavior. Numerical simulations of a typical 3-storey structural unit in the Potala Palace are studied. The acceleration responses of the structure under the action of El-Centro seismic waves are studied. Results show that the arrangement of the joints is helpful for seismic resistance of the structure. Most Tibetan ancient timber structures are suffering from different types of damage to certain extent which is vulnerable to seismic actions. Typical damage problems of the structural components are summarized and the main causes of this damage are analyzed. Different rehabilitation methods that can be implemented are discussed, providing references for maintenance of the structures. [ABSTRACT FROM AUTHOR]