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RE: Cross-grain Compressive Strain in Timber

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Jake, Thor


I think Thor was looking for the properties perpendicular to the grain. The E value given in the codes is typically for loading parallel to the grain, and mostly a flexural modulus. The Australian code does provide bearing strengths(stress) for loading parallel and perpendicular to the grain, for various strength groups, I assume NDS also does . Wood is a naturally occurring  fibre reinforced polymer composite: for a composite parallel loading produces isostrain, and transverse loading produces isostress (for matrix and fibres): from which can determine an effective E for the composite. But then need properties of the wood matrix and fibres, and distribution of the fibres since not all fibres are continuous throughout. Hence reason for testing actual material.


Base plate problem or end plate problem? Beam on elastic foundation? Where a beam is connected by end plate to a column flange,  then yielding of column flange is more the issue, or maybe column end plate to beam flange. But then have bolts straight through. I guess using screws into timber may make it more of a base plate problem, but timber beam still more a flexible plate than the great mass of concrete below a base plate. Also bolts seems a better choice for holding guard rail posts in place, since screws would have a tendency to work their way out of the timber if loaded in tension. Most details I’ve seen tend to have posts down to ground, or fasten posts to side of floor bearers and/or floor joists (eg. the member normal to the guardrail).


Once guard rail posts fastened to face of timber beam: how good is the timber plank in torsion?



Conrad Harrison

B.Tech (mfg & mech), MIIE, gradTIEAust



South Australia