Decay Effect On Mechanical Properties Of Ancient Architectural Timber Structure

Timber structure is the traditional form of ancient Chinese architecture, many existed ancient timber architectures have a history of thousands of years. As one of the natural defects of timber, decay defects are common among timber architectures, and it has a great influence for the bearing capacity of the ancient buillding structures. It is of great significance for protection of ancient wood structure buildings to research the effect on mechanical properties caused by decay. Based on this, the main research contents and innovation points of this article mainly includes the following several aspects:1) Come up with a method to detect mechanical parameters of decay timbers of different classification. For the protection of cultural relics, Ancient structure generally does not allow for destructive detection. Ultrasonic testing technology is a kind of wood nondestructive testing technology, it can testing the structure without destroying it, and the testing process is simple, the operation is convenient. It has been widly used in the tests of modern concrete structure and steel structure. To testify the feasibility of using ultrasonic detector to inspect mechanical parameters of decayed wood, according to the national standard, The author using ZBL-520 type nonmetal ultrasonic detector, to wave as a parameter, calculated equivalent elastic modulus of the small specimens-which are removed from Nanjing Heaven temple, then together with the actual elastic modulus of the small specimens for regression analysis. It proved the feasibility of this method to inspect mechanical parameters of decayed wood.2) To verify the method to use ultrasound combined with finite element numerical simulation getting ultimate bearing capacity of decay timbers is feasible. In order to get the ultimate bearing capacity of the decayed wooden parts, we use 10 speciments of timber beam and timber pillar respectively for experement. firstly, layout measure points, using ultrasonic detector totest the mechanical parameters of each measure point. Then do bearing test with these large components in universal testing machine. Make comparison with the simulation results of the finite element software artifacts ultimate bearing capacity. It proved the feasibility of this method to predict the actual bearing capacity of the decayed wooden parts.3) Come up with specialized reduction factor to consider decay influnce on the bearing capacity of timbers. On the basis of the above research, the author analysis the different influnce on the bearing capacity of timber caused by different kinds of decay, and discusses the decadent location, decayed depth and decayed classification effects on the bearing capacity of wooden beams and wooden pillars respectively. At last, considered that the existing specifications have fewer provisions for the influnce on the bearing capacity of decayed wood, the author come up with specialized reduction factor to consider this.