Abstract: [Objective] The effects of cross section, loading mode and finger-joint type on the bending property of larch structural finger-jointed lumber in large dimension was studied. Then the characteristic values under the different experimental factors (cross section, loading mode and the finger-jointed type) were obtained. These are very important to the domestic researches of the bending property of larch structural finger-jointed lumber in large dimension.[Method] According to LY/T 2228-2013, larch (Larix gmelinii) timbers of grade Ⅱc with two different cross section (40 mm×90 mm and 40 mm×140 mm)were chosen to fabricate the structural finger-jointed lumber. The statistical methods were used to do normality test and homogeneity of variance test, and two-sample t test was applied to check whether experimental factors (cross section, the loading mode and the finger-jointed type) significantly influencing the modulus of rupture (MOR) and modulus of elasticity (MOR) of larch structural finger-jointed lumber in large dimension.[Result] The experimental factors (cross section, the loading mode and the finger-jointed type) had significant effect on the MOR and MOE in some particular situations. The cross section had significant effect on both MOR and MOE of the samples with V finger-jointed type and narrow side loading mode. Concretely, this effect was that MOR and MOE of the samples with large cross section (40 mm×140 mm) were higher than those of the samples with small cross section (40 mm×90 mm). The difference in loading mode did not behave significant effect on the MOR. But the loading mode obviously influenced the MOE of the samples with large cross section (40 mm×140 mm) behaving that the values of MOE tested in the narrow side loading mode were higher than those of the large side loading mode. The finger-jointed type also significantly influenced MOR of samples with large cross section (40 mm×140 mm) and large side loading mode. In details, the MOR of the samples with V finger-jointed type was higher than that of the samples with H finger-jointed type. The finger-jointed type had significant effect on both MOR and MOE of the samples with small cross section (40 mm×90 mm) and narrow loading mode. So the MOR and MOE of samples with H finger-jointed and narrow loading mode were higher than those of V finger-jointed one. On the basis of the data obtained from the bending property test of larch structural finger-jointed lumber in large dimension, parametric approach and nonparametric approach were separately used to estimate the property values, and the property value obtained through parametric approach was smaller than that obtained through nonparametric approach.[Conclusion] Larch finger-jointed lumber is suitable for using as wooden engineering material. The large side loading mode and V finger-jointed type and appropriate cross section will be favourable to guarantee the bending properties of structural finger-jointed lumber. When the structural finger-jointed lumber with large cross section are bended under narrow side loading mode, the MOR and MOE could be more easily influenced by loading mode and finger-jointed mode. So the structural finger-jointed lumber with large cross section is not recommended when the flexure strength is assured. The usage of structural finger-jointed lumber as narrow side loading mode should be avoided too, because the narrow side loading mode is also very easily influenced by the experimental factors. The nonparametric method is suggested to estimate property value of bending property. When the sample size is not sufficient, the property value calculated through parametric approach will be lower than that calculated through nonparametric approach. So in this situation the minimum value in all property values that calculating by both parametric and nonparametric methods is more suitable for the property value.

Key words: structural finger-jointed lumber, flexural property, large dimension, property value