Experimental Investigation of the Longitudinal Pure Compression Behaviour of Full-Scale Radiata Pine Solid Sawn Timber Boards with Intermittent Lateral Restraint

• 108 full-scale restrained timber boards were experimentally investigated. • Three distinct types of stress-strain relationships were identified. • A bilinear softening model was proposed. • Timber grade influenced ductility with higher grades showed reduced ductility. • A new predictive model for compression strength was developed. Solid sawn timber is increasingly used in structural applications due to its sustainability, mechanical efficiency, and adaptability in modern construction. Despite its widespread use, understanding of pure compression behaviour and fracture characteristics of full-scale boards remains limited. This study investigates the pure compression behaviour of full-scale Radiata Pine boards subjected to intermittent lateral restraint. A total of 108 specimens, with dimensions of 35 × 90 × 2720 mm and grades F5, MGP10, MGP12, and MGP15, were tested to evaluate longitudinal compressive strength, modulus of elasticity, peak strain, ultimate strain, ductility, stress-strain response, and failure modes. Results showed that the average compressive modulus of elasticity ( E c ) was lower than the edgewise modulus of elasticity ( EMoE ), while both peak strain ( ε c,0 ) and ultimate strain ( ε c,0,u ) were lower than those for short boards. Three distinct stress-strain response types were observed, and a bilinear softening model was proposed to best represent both pre-peak and post-peak stages. Higher-grade boards exhibited lower ductility, indicating a more brittle failure behaviour. Finally, a new predictive model for compressive strength was developed, achieving an R² of 0.85, and demonstrating enhanced predictive performance relative to existing models.