古建筑旧木材腐朽状况皮罗钉检测结果的定量分析

Quantitative Analysis of Decaying Detected by Pilodyn in Wood of Ancient Architecture

以故宫武英殿维修时替换下来的局部腐朽的落叶松、软木松旧木构件为材料,用目测法将试材划分为未腐朽及4级腐朽,共5个等级,对不同腐朽等级木材进行皮罗钉径向、弦向检测后,测定木材密度。应用统计学方法分析密度与皮罗钉径向、弦向打入深度间的关系,建立木材密度与皮罗钉打入深度的回归模型,以探讨应用皮罗钉检测方法定量评估古建筑木材材质状况的方法和途径。结果表明:随着木材腐朽程度的加深,木材密度降低,径向、弦向打入深度显著加大,各腐朽等级间差异极显著。2个树种因腐朽引起的密度及径向和弦向打入深度变化趋势表现出高度的一致性,达到"4"级腐朽时,与未腐朽材相比,密度降低20%左右,径向和弦向打入深度增加110%～136%;皮罗钉径向打入深度与弦向打入深度之间存在极显著的线性函数关系,密度与皮罗钉弦向打入深度及径向打入深度之间均存在着极显著的幂函数关系,决定系数均在0.01水平显著(P<0.01);落叶松和软木松密度与弦向打入深度的相关系数分别为-0.67和-0.76,均大于密度与径向打入深度的相关系数-0.55和-0.69。

The displaced and partially-decayed larch and pine timber frames from the Hall of Military Prowess,the Palace Museum,were collected and visually classified into five categories of decaying. After measuring the radial and tangential penetrations with Pilodyn,the classified wood samples were determined for wood densities and the relationships between Pilodyn values and wood densities were analyzed from measurements of 125 larch samples and 60 pine samples. The regression models of wood density as function of Pilodyn values were used for assessing the feasibility of quantitative analysis of wood quality in ancient architectures. The results showed that wood density decreased and the Pilodyn values increased with degree of decaying and there existed significant differences in wood density and the Pilodyn values among the decay classes. The wood density variation and the Pilodyn values variation of radial and tangential penetrations with decaying were highly consistent between the two wood types. For the wood samples of decaying category 4,their densities decreased 20%,and radial and tangential penetrations increased 110% ～ 136%,compared with non-decayed wood samples. There were significant linear correlations between the tangential and radial penetrations of Pilodyn,and significant power function relationship between wood density and tangential penetration,and between wood density and radial penetration for both wood types（P〈 0. 01） ,the values of correlation coefficient,r,were-0. 67 for larch and-0. 76 for pine for the relationship between wood density and Pilodyn values of tangential penetration,and-0. 55 and-0. 69 for the relationship between wood density and Pilodyn values of radial penetration.