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.
This paper describes results and analysis of experimental testing of entire and partial compression strength and stiffness parallel to the grain of solid timber (Japanese cedar). To investigate the spreading effects, the size effect of strength and stiffness, and the mechanism of the damage zone located close to the loading plates, tests on 90 specimens were performed. As a result, it was observed that damage zones existed near the loading plates. The observed spreading effects in the compression parallel to the grain were very small which justifies neglecting them regarding strength and stiffness. Although a presence of a size effect of the compression strength parallel to the grain of glulam specimens with knots was reported, the compression strength parallel to the grain of solid wood specimens without knots does not have a size effect. The height and width of the cross-section of the specimens have an influence on the damage zones and, hence, on the effective modulus of elasticity of the full height of the specimens. The compression strength has a correlation with the density of the timber and the width of the annual rings.
In this study, we tested for identifying dimensional effects of rotational stiffness of wedged and halved scarfed joint. At first, a model of stress distribution in bending was made from observation of joints fracture under four-point bending tests. Proposal of rotational stiffness design formula(M �) was derived from this model. Under the tests, M � equation values well corresponded to all types of experimental ones. In particular, rotational stiffness rose in proportion to the cube of the materials height and the cogging width and had asymptotic limit value. These tendencies corresponded to the experiment results.
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