Strength of bolted timber joints subjected to lateral force
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Timber, its use and conections. Upcoming SlideShare.
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- Mechanical and physical properties of three timber species of potential structural use in Rwanda.
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Like this presentation? Why not share! Embed Size px. Estimates of the mean and the near-minimum values of small, clear samples of wood were obtained using the international testing standards ISO.
The Institute of Materials, Minerals and Mining
An indepth review of current sampling techniques used in wood engineering strongly suggests that the random technique of sampling and its variations remains a reliable technique which, when designed properly, will yield accurate estimates. Several samples of the three timber species chosen by using the random technique of sampling were tested for both the physical density, specific gravity, swelling and shrinkage characteristics and the mechanical properties bending strength and stiffness, compressive strength parallel to grain, tensile strength parallel to grain and shear strength parallel to grain using universal testing machines available both at the National University of Rwanda UNR and at Marquette University.
Unadjusted for end use data were obtained in the unseasoned and at 12 percent moisture content.
A randomized two factor factorial analysis was performed in an effort to quantify the effects of a particular species and the forest location from where it was sampled on the value of the property mean. The conclusion reached was that not enough evidence existed to support or reject the hypothesis that forest location and species have any effect on the strength values of the wood sampled.ualapolri.tk
Strength properties of wood | IOM3
Using the Australian and the Andean Pact Structural Grading Rules and data obtained in this study, a grading rule is proposed for structural lumber in Rwanda. This Grading Rule describes three structural grades based upon the tolerance limits established on the strength-reducing factors. Each piece is first subject to visual grading, then it passes through the machine which bends the piece to a predetermined curvature and measures the force required to bend deflect it. The grading of yard lumber is based on the intended use of the particular grade and is applied to each piece with reference to its size and length.
These are graded with respect to its strength in bending when loaded on the narrow face. These are graded with respect to its strength in bending when loaded on the narrow face as a joist or on the wide face as a plank.
These are graded primarily as posts and columns carrying longitudinal loads, but adapted for miscellaneous uses in which strength in bending is not especially important. The finishes designations of lumber are based on the roughness or smoothness of its surfaces. Most lumber used in building design is surfaced on both the faces and on both edges and is referred to as S4S surfaced on four sides.
If a designer specifies a nominal size of lumber but does not define which faces to be finished, the material supplied will most likely be S4S. If some of the combination of surfaced and rough faces is desired, the designer may specify it. Other combinations are defined by symbols S for sides and E for edges. Examples of these combinations include S2S1 E surfaced on two sides and one edge , S2S surfaced on two sides only , S1S2E surfaced on one side and two edges , etc.
Planning reduces the nominal sizes, the amount of reduction depending upon the size. Dressed timber is adopted when it is exposed to view has to be dress.