Quantitative analysis on the detected results by resistograph on inside wood decay of ancient architecture

Five replaced partially-decayed Larix spp.timber frames from the Hall of Military Prowess,the Palace Museum,were collected and visually graded into five levels of decay to study the relations between resistance value measured by resistograph and air-dried density,bending strength and compressive strength parallel to grain respectively.The regression models were established and proved for different decay levels with 319-group samples.The results showed that wood density,bending strength,compressive strength parallel to grain and resistance values decreased evidently with the increase of decay degree,and there existed significant differences among four decay levels.The remaining value percentage of four indices at the third decay level were 24%,42%,76% and 71%,respectively.Significant linear correlation existed between resistance values and the other three indices at 0.01 level,and the correlation coefficient(r) presented the biggest value between resistance values and density.The regression model between resistance values and physi-machanical properties was established by 284-group data,and it was proved with 35-group samples of different decay levels.The results show that there are no significant differences between the predicted values by the regression model and the real values at both 0.05 and 0.01 levels.