Study On The Variety And The NDE Of Aged Wood Physical And Mechanical Properties Of Ancient Architecture

The test specimens of larch(Larix sp.),pine(Pinus sp.), spruce(Picea sp.)and fir(Cunninghamia lanceolata)were obtained from demolished wooden framework aged 50~135 years in Forbidden City-wuyingdian. Wood density and mechanical properties were measured with small test specimens of not-rotted and rotted wood. The changes of not-rotted wood physical and mechanical properties were studied and decay attenuation of different degrades aged larch and pine wood was obtained. The test results of Resistograph were analyzed quantitatively and the relationships between dynamic Modulus of elasticity (MOE) tested by Fast Fourier Transform (FFT) inspection and mechanical MOE and modulus of rupture (MOR) were discussed. The main research conclusions were summarized as following:1. The wood density and mechanical properties of not-rotted aged larch, pine and fir were declined, but those of not-rotted aged spruce wood were increased. And the properties of healthy pine in 2004 were the same with not-rotted aged pine after using 135-year.2. Wood density and mechanical properties were rapidly decreased with the increasing decay for larch and pine timber, the most is MOR, then crushing strength, and the density is the smallest. The residue rate of MOR was about 30% for two kinds of wood, and the residue rate of crushing strength were respectively about 40% and 50%.3. The results showed that there were significant positive correlations in wood density,MOE,MOR and crushing strength of larch, pine and spruce.4. Three sections were divided analyzing the change of resistance by Resistograph, namely, trough, peak and average section. The results of three sections among different grades decay were markedly distinct. A reduce tendency exhibited by rate of attenuation was consistent, and the diversity of attenuation rate was not remarkable along with gradual increase of decay. Significant positive correlations at 0.01 1evel were exhibited between the trough and wood density, MOR, crushing strength. The difference of the peak and average and wood density, MOR reached 0.01 level of significance, and crushing strength reached 0.05 level of significance.