Strength Properties Of Timber Research Articles

Some physical, mechanical and anatomical characteristics of stemwood and branchwood of two hardwood species used for structural applications

Interest in branchwood utilization is gradually increasing on account of increasing demand for wood for construction and furniture production. However, wood quality assessment involves consideration of physical, mechanical and anatomical characteristics. This present study compared density, MOE and MOR, and compressive strength at 17 ± 3 %MC and 10 ± 4 %MC and some anatomical characteristics of Khaya ivorensis and Entandrophragma cylindricum by following BS (British Standard) 373, Strength properties of timber 1–24, 1957; ISO (International Standard) 3131, International Standard; wood-determination of density for physical and mechanical tests, 1975) and IAWA committee protocol of 1989. Branchwood and stemwood samples were extracted from two natural forest reserves. Results indicated that branchwood of the species dried to 17 %MC and 10 %MC proved to be as good materials as their stemwood counterparts in terms of bending and compressive strength parallel to the grain. Branchwood had significantly (p < .01) higher density than stemwood but such high densities did not translate into significant higher strength values. Moisture content and wood types (stemwood or branchwood) had significant effect (p < .001) on density, MOE, MOR and compressive strength. Fibre and axial parenchyma quantities were, respectively, the highest and lowest in both stemwood and branchwood of the two species. Fibre proportions in stemwood and branchwood correlated positively with density, MOE, MOR and compressive strength. Compared to bending strength, compressive strength was less influenced by anatomical properties of stemwood and branchwood. It was concluded that branchwood of E. cylindricum and K. ivorensis are not inferior to their stemwood and therefore could be used for structural applications. Further studies including shear strength, adhesive bonding, and finishing properties should be carried out to confirm the possibility of utilising branchwood for structural applications.

非正規確率楕円による木材強度データの&lt;b&gt;2&lt;/b&gt;次元表現（第&lt;b&gt;1&lt;/b&gt;報）

ヤング率と曲げ強度といった構造材の強度特性間の確率論的な関係を利用すると，しばしば有益な結果がもたらされる。例えば，機械等級区分法の導入により合理的な基準強度の設定が実現された。実大材の強度特性間の2変量非正規分布データを解析するには，統計的で視覚的な表現方法が必要となる。確率楕円は指定された内包確率で2変量分布を描画する方法であるが，非正規分布には適さない。そこで，本報では非正規周辺分布を持つ歪んだ確率楕円の描画方法について報告する。この方法は，周辺分布に基づく等確率変換によって，通常の確率楕円を分位等価な非正規確率楕円に変換する。実大材の曲げ試験の蓄積データ群を用いた数値実験により検証したところ，楕円の内包確率の正確さ，無相関化変換された偏角に対する確率の均質性，およびデータ群間の比較性について，良好な性能を示すことが確認された。

非正規確率楕円による木材強度データの&lt;b&gt;2&lt;/b&gt;次元表現（第&lt;b&gt;2&lt;/b&gt;報）

非正規確率楕円による木材強度データの&lt;b&gt;2&lt;/b&gt;次元表現（第&lt;b&gt;2&lt;/b&gt;報）

MECHANICAL BEHAVIOUR OF TIMBER‐TO‐CONCRETE CONNECTIONS WITH INCLINED SCREWS

The purpose of this paper is to adopt the Johansen's yielding theory as a possibility to predict the ultimate load for timber‐to‐concrete joints using self‐tapping threaded connectors screwed at an angle into the wood. The ultimate load‐bearing capacity of a single connector is predicted to be when either the stresses in the wood reach the plastic failure stress level or when a combination of plastic failure in wood and dowel is attained. K. W. Johansen assumed that no axial tension occurred in the dowel and, thus no frictional contribution affected the lateral load‐bearing capacity. However, the joints with inclined fasteners are first affected by tension load, so the withdrawal capacity of the screws has to be taken into account. In order to determine the load bearing capacity for specific connector geometry, the kinematical possible failure modes are determined. The screw in the concrete part of connection was taken as rigidly embedded and thus no deformations appeared. The study showed that the load‐bearing capacity for connections with inclined high tensile strength screws can be predicted using the yielding theory, but this theory was unable to predict precisely the failure mode. Possible reasons for that include limited fastener ductility and influence of the screw inclination on the strength properties of timber.