Study on Strength of Glued Laminated Timber Beams With Round Holes

Abstract

At present, few strength evaluation methods have been established for timber beams containing round holes but several have been proposed in Japan and overseas. However, it is not clear whether the method can be applied to glued laminated timber composed of heterogeneous material grades mainly used for beams in Japan and elsewhere. In this paper, we experimentally verify that the proposed strength evaluation method can be applied to glulams. Moreover, we verify that the strengths of glulams that also contain round holes can be estimated using finite element analysis.

Study on the strength of glued laminated timber beams with round holes: difference in structural performance between homogeneous-grade and heterogeneous-grade timber

“…The results of the bending tests of beams, material experiments and experimental specification FEA for glued laminated beams composed of heterogeneousgrade timber are the same as those reported in [8]. In this paper, a new study conducted on glued laminated timber beams composed of homogeneous-grade to determine the difference in structural performance between homogeneous-grade and heterogeneous-grade glued laminated timber beams with round holes in comparison with the results reported previously is presented.…”

“…In Japan, glued laminated beams composed of heterogeneous-grade timber, as specified in Japanese Agricultural Standard (JAS) [7], are very often used as beams, and it is not known whether the presented design codes and design proposals [1][2][3][4][5][6] can be used. Therefore, in [8], it was confirmed that the stresses acting on a hole in a glued laminated beam composed of heterogeneous-grade timber can be accurately estimated by finite element analysis (FEA) to estimate the load-bearing capacity associated with fracturing due to cracking. In [8], a design equation was proposed to compensate for the average length of the mean stress method [9] (Fig.…”

“…Therefore, in [8], it was confirmed that the stresses acting on a hole in a glued laminated beam composed of heterogeneous-grade timber can be accurately estimated by finite element analysis (FEA) to estimate the load-bearing capacity associated with fracturing due to cracking. In [8], a design equation was proposed to compensate for the average length of the mean stress method [9] (Fig. 2), a generalization of linear elastic fracture mechanics, to take into account the size effect of the portions of the design with large tensile stresses (Eqs.…”

“…3 Test specimens and specifications H/10 (H = 300 mm only) and H/15 (H = 450 mm only). In [8], we conducted bending tests on glued laminated timber composed of heterogeneous-grade with D/H of 2/3 and 4/5, but since it is considered difficult to incorporate glued laminated timber with large hole diameters into the design code, these D/H values were excluded from this study. The number of test specimens is two for each type of glued laminated beam composed of homogeneous-grade timber and three for each type of glued laminated beam composed of heterogeneous-grade timber.…”

“…Equations (1, 2) can be used to estimate the bearing capacity related to small and large holes during crack-related fracturing. The analysis in [8] shows that the stress acting on the hole is smaller in the case of a glued laminated beam composed of heterogeneous-grade timber than in the case of a glued laminated beam composed of homogeneous-grade timber:…”