Experimental study on partial compression parallel to grain of solid timber

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.

Automated summary

The experimental testing of compression strength and stiffness parallel to the grain of solid timber revealed that the presence of knots in glulam specimens resulted in a size effect, while solid wood specimens without knots did not exhibit this phenomenon. The height and width of the cross-section of the specimens were found to influence the damage zones and effective modulus of elasticity. Additionally, compression strength was correlated with timber density and annual ring width.