Probabilistic characterisation of the density, bending strength, and stiffness of timber structural elements from historic buildings

This paper presents probabilistic models for the density, modulus of rupture, and modulus of elasticity of historic softwood structural elements based on non-destructive testing data. Several probability density functions were fitted to experimental results obtained from three species of the genus Pinus — Pinus sylvestris , Pinus nigra , and U.S. southern yellow pine— and compared with the probabilistic models recommended by the Joint Committee on Structural Safety (JCSS) for contemporary timber. The results reveal significant differences between the proposed and JCSS models, highlighting the need to account for both species and age (historic versus contemporary) when statistically characterising timber properties. The study confirms that well-preserved historic timber can retain mechanical properties comparable to those of modern wood. The proposed species-specific probability density functions provide a more accurate basis for the probabilistic analysis and reliability assessment of historic timber structures, supporting their preservation and the broader goals of cultural heritage conservation and sustainable construction.