Anistropic plasticity and the notched wood shear block

The American Society for Testing and Materials notched wood shear block specimen is revisited for use with laminated strand lumber. Shear block tests on fully oriented and randomly oriented panels were conducted to determine shear strength in each of the orthotropic planes. Nominal shear strengths are reported from experimental results. A three-dimensional finite element analysis was conducted to determine the ultimate shear strength of the shear blocks by accounting for the non-uniform stress distribution and stress concentrations developed in the blocks. The anisotropic plasticity material model accounts for non-linear behavior in compression. Brittle failure was predicted using the Weibull weakest link theory for each of the six tension and shear stresses. The model produced similar load-displacement results to the experiments and was compared against experimental ultimate strengths and failure modes. Model strength predictions were found to be approximately 1.7 times greater than the nominal shear stress determined for the assumed shear plane in experiments. This indicates conservative strength predictions from experiments. The model showed the stress concentration factor at the notch to be at least 2. The stress concentration, combined with the fact that a mixed failure mode exists (i.e., shear and tension perpendicular to the grain) results in poor estimates of the shear strength. The influence of shear modulus, G, on model-predicted results was investigated. It was shown that the load-displacement behavior for in-plane shear was least affected by the in-plane G, whereas G in the other planes only mildly influenced load-displacement, ultimate strength, and stress concentrations.

You must be logged in to download any documents. Please login (login accounts are free) or learn how to Become a Member