A semi-destructive assessment method to estimate the residual strength of maritime pine structural elements degraded by anobiids

In this article, an assessment method to estimate the residual strength of pine structural elements degraded by anobiids is presented. This novel method was developed in the laboratory to be used in situ and is based on the strength required to withdraw a screw on the surface of degraded timber. Samples of degraded maritime pine (Pinus pinaster Ait.) were submitted to micro-computed tomography (μ-XCT) to quantify density loss. This parameter is highly correlated with mechanical properties thus central for the assessment of timber structural capacity. Density loss values have been correlated with both screw withdrawal force and shear parallel to the grain strength showing significant relationships between these parameters. Using these correlations, the density loss of a degraded element and its shear strength parallel to the grain via the screw withdrawal force can be estimated enabling a valid quantitative assessment of the timber elements residual strength and, therefore, contributing to reduce unnecessary replacement, to boost eco-efficient interventions and to provide foundations required to perform experimental modelling tests.