落叶松目测等级规格材顺纹抗压强度尺寸效应

Effect of Size on Ultimate Compression Strength Parallel to Grain of Visually Graded Chinese Larch Dimension Lumber

关键词:  落叶松  目测等级  规格材  顺纹抗压强度  尺寸效应

Key words:  Chinese larch  visual grade  dimension lumber  ultimate compression strength(UCS) parallel to grain  size effect

摘要:

以落叶松规格材为试验对象,研究了不同目测等级下该规格材截面宽度与其顺纹抗压强度之间的依存性.试验选取1 630根目测等级规格材,分成高、低目测等级组.测试6.5，9.0，14.0 cm三个宽度试件的顺纹抗压强度,并利用斜率法和形状参数法求得高、低目测等级组顺纹抗压强度5%分位值的宽度尺寸效应系数.结果表明：用斜率法获得高、低目测等级组试件顺纹抗压强度5%分位值的宽度尺寸效应系数分别为0.11，0.20；该宽度尺寸效应系数可以应用于落叶松规格材强度的宽度尺寸调整；对于低目测等级组试件,用形状参数法估计的参数与用斜率法求得的宽度尺寸效应系数的倒数近似.

Abstract:

Size effect is one of important factors to adjust tensile strength of dimension lumber to an desirable property. The dependence of the ultimate compression strength on the width of Chinese larch visually graded dimension lumber was investigated. 1 630 dimension lumbers were parted into two groups of high visual grades and low visual grades; three lumber widths(6.5 cm, 9.0 cm and 14.0 cm) were selected and ultimate compression strength property was tested. The width effects of the 5th percentile of ultimate compression strength were estimated by the slope method and the parametric method. Using nonparametric estimates, the estimated width effect parameters of high grade(H) and low grade(L) were 0.11 and 0.20 for the 5th percentile. The parameters of L were larger than those for H. The width effect could be used when using the dimension lumber for practice purposes. When two parameter Weibull distribution functions were fitted to the strength data, the estimated shape parameters of the Weibull distribution by the parametric method were almost identifical to the inverse of nonparametric parameters for the L grade.