Buckling of adhesive-free Wooden-Dowelled Cross-Laminated Timber panels

Cross-Laminated Timber (CLT) has evolved from a niche product to a widely used building material, the manufacture of which still depends on synthetic adhesives with recyclability and environmental concerns. Adhesive-free alternatives using hardwood dowels offer greater sustainability, yet their global stability, especially at high slenderness, is not well understood. This study explicitly addresses the axial buckling behavior of adhesive-free Wooden-Dowelled Cross-Laminated Timber (WDCLT) panels and compares them with Glued Cross-Laminated Timber (GCLT) panels. Additional knowledge gaps include the effects of interlaminar slip, rolling-shear cracking, delamination, and geometric imperfections, as well as a lack of large-scale test data for model validation. This paper addresses these gaps through a combined experimental investigation on eight adhesive-free WDCLT panels, each 2 m high, with five and seven plies. The bending stiffness of each specimen was preliminarily measured under controlled moisture conditions, followed by axial buckling tests under concentric and eccentric loading (eccentricity e = t/6). The onset and progression of delamination and rolling-shear damage were monitored using vision-based tracking techniques, and the influence of initial geometric imperfections was assessed for both loading conditions. The results were then compared with those obtained from equivalent GCLT panels. Key mechanical parameters were measured or inferred, including bending stiffness (EI), critical axial load/capacity, lateral deflection, and vertical displacement. A reduced-order, analytical ODE model within the Eurocode 5 framework is proposed, including a quadratic-quadratic N-M interaction domain and WDCLT-specific inputs (EIexp, imperfection amplitude) to compute the critical axial load for concentric and eccentric compression.