2021-10-19T13:48:59Zhttps://soar-ir.repo.nii.ac.jp/oaioai:soar-ir.repo.nii.ac.jp:000112032021-03-01T11:55:19ZMechanical Properties of Full-sized square lumbers of Karamatsu長野県産カラマツ造林木の実大強度性能徳本, 守彦35048武田, 孝志35049中野, 達夫35050橋爪, 丈夫35051吉田, 孝久35052武井, 富喜雄35053長尾, 博文35054田中, 俊成35055中井, 孝35056Bending, compressive and tensile strength of Japanese larch (Larix leptolepis Gord.)were investigated on full-sized square sawn lumbers from Nagano Prefecture.Testing trees were collected from 7 stands : A : Usuda (44 years old), B : Hase (50 years old), C :Usuda (44 years old), D: Hase (42 years old), E: Ooshika (44 years old), F: Higa-shimata (40 years old), G: Nyuukasa (75 years old). Three types of square lumbers (I : boxed heart square, II: square having two sides of quarter sawn grain and III: squre having 4 sides of quarter sawn grain) were cut from testing trees according to the diameters of the top ends of each cut wood. The nominal specimen was 120×120×3000mm.All specimens were in the air-dry condition. These square lumbers were divided into two groups, bending specimens (315 pieces) and tensile spesimens (260 pieces). Specimens for compressive test (540mm length) were cut from the sound portions of bending specimens which failed by bending test. Before the breaking test, dynamic moduli of elasticity were measured by the four kinds of non-destructive testing methods. The main results obtained are as follows. 1) Bending strength (MOR)The average MOR of squars in stand A is the highest and the average tends to increase with increasing tree age. However, that of stand G is not the case because the growth of trees is not good owing to the high altitude. The average MOR of squares from stand E is second in the order in spite of good growth. This is because the testing trees in stand E frequently had some reaction wood and were affected significantly by wind. The average MOR becomes higher in the order, square I, square II, square III and becomes lower with increasing of the number of cut wood. Generally, the correlation are high between MOR and the maximum single knot size ratio (KDL) at the surface of tension side / the distance from the pith to the surface of tension side of the specimens. 2) Short column compressive strength (δc) The average δc becomes higher in the order, stand E (377 kgf/cm2), stand B, G, A(333～322 kgf/cm2), stand F, C, D (298～294kgf/cm2). The correlation is not clear between δc and tree age of stand. δc becomes higher in the order, square I, square II, squares III and becomes lower a little from the first cut to the higher number of cut wood. However, the effects of the sawing pattern and the difference of height in the testing tree is significantly small compared with MOR. It can be considered that δc basically depends on the density of squares. But, it cannot deny that δc tends to decrease with increasing KDL. 3) Tensile strength (δt) The average δt is lower in the order, stand A : 288kgf/cm2, stands F, G, B : 233～221kgf/cm2, stands C, D, E : 212～205kgf/cm2. Squares from stand A with tree age of 75 years are 7% higher in the sensity, 9% higher in tensil youngs modulus and 30% higher in δt than that of stand G with age of 65 years in spite of having wider annual ring widths than stand G. Generally, the statistical significant correlation was not found between δc and the sawing patterns, the position of cut in the testing trees. 4) Relative relation among MOR, δc and δt. Relative relation of the values of 5th%ile of bending: compression: tension of squares Japanese larch is 1.00: 0.82: 0.51. The relative value of 5th%ile of δt is lower a little compared to the case of sugi (Crytomeria japonica D.Don). The squares from stand A has the highest strength in bending/tension and the second highest in compression among the 7 stands. So, it is considered that stand A is the best. The squares from stand E is the highest in compression and the second highest in bending. However, that of stand E have significantly low δc. So, it is considered that the stand E is peculiar and under adverse condition. 5) Relation between the strength and the various parameters of wood quality a) The correlation is not so high between MOR and KDL, the maximum group knots size ratio (SKDL). However, the correlation is high between MOR and KDL/SKDL at the surface of tension side of specimens. Also, the correlation is high between MOR and the distance or the number of annual ring from the pith to the surface of tension side of specimens. It can not be considered that annual ring width (ARW) gives good results for estimating MOR in practices. b) Although the week corelation was found between δc and KDL, it is obvious that measuring knot size could not work effectively for estimating δc in practices. c) The correlation is not so high between ac and KDL, SKDL. 6) Relation between strength and dynamic Young's moduli The correlation is high between MOR and the dynamic Youngs moduli obtained by the non-destructive testing methods. For the purpose of grading sawn lumbers, it can be chosen any method among deflection, ultrasonic wave propagation time, stress wave propagation time and fundamental vibration frequency. Especially, the correlation is high between MOR and the moduli by the longitudinal vibration method. The compressive and tensile strength could be estimated by all moduli of elasticity same as the case of MOR.Article信州大学農学部演習林報告 33: 75-145(1997)departmental bulletin paper信州大学農学部附属演習林1997-03-25application/pdf信州大学農学部演習林報告33751450559-8613AN00121330https://soar-ir.repo.nii.ac.jp/record/11203/files/Agri_Forests-33-02.pdfjpn