Effects of beetle attack on the bending and compression strength properties of pine wood

Abstract

One major difficulty one has to face in the assessment of old timber structures concerns the assessment of the effective strength of timber cross sections with biological damage. Its effects may generally be considered, either by assuming a reduced cross section or by assuming reduced mechanical properties for the apparent cross section. Where beetles attack produce a “diffuse” damage, i.e. their tunnels spread in most of the cross section surrounded by a significant amount of undamaged wood, the assumption of a reduced cross section may not be the best approach. To assess the effect of diffuse damage by beetles to pine timber, damaged timber was collected from an old structure and tested in bending and compression in small “clear” wood specimens(cross sections of 2cm x 2cm). The varied degrees of biological damage were assessed in terms of the “holes” area measured in the cross section surface with the help of image processing analysis. Bending and compression strength were correlated with biological damage. Test results suggest that, although very high levels of insect destruction have an impact on the timber strength, timber density still is the governing factor.