Deformation level and specimen geometry in compression perpendicular to the grain of solid timber, GLT and CLT timber products

Compression Perpendicular to Grain (CPG) is a crucial aspect of timber design, particularly with the advent of engineering wood products like Cross Laminated Timber (CLT), often used in point-supported structures. After many years of discussion, the mechanics-based model by Van der Put has finally been included in the new Eurocode draft. This model offers a more systematic approach to design with a solid theoretical foundation for stress dispersion. However, there is still a need for improvement, especially in two areas: accounting for the capacity increment associated with increasing levels of deformation and determining the maximum effective height to be assumed in calculating the load spreading in deep timber elements. In this paper, the authors focus on these two areas of improvement for GLT, solid timber and CLT timber products. They analyse the data of two extensive experimental campaigns conducted at Norsk Treteknisk Institutt (Norwegian Institute of Wood Technology) and at the Norwegian University of Science and Technology (NTNU) on Glued Laminated Timber (GLT), Solid Timber (ST) and CLT. Additionally, they validated a parametric finite element (FE) model in Abaqus to assess the effect of the height of the timber element on stress distribution. A parametric approach developed in Abaqus aims to find the optimal height threshold to be assumed in the new code formulation. • An extensive experimental campaign on ST, GLT and CLT is conducted. • Support type, load position, load plate size and loading scenario influence is analysed. • The capacity increment associated with increasing levels of deformation is assessed. • A linear dependence of the average capacity on the deformation level was observed. • The maximum effective height to be assumed in calculating the load spreading is determined.