Numerical modelling of moisture-driven frictional interlocking in adhesive-free CLT panels

Wooden-Doweled Cross-Laminated Timber (WDCLT) offers an adhesive-free alternative to conventional CLT, enhancing circularity and environmental performance. However, its structural response is significantly governed by the frictional interaction between timber lamellae and wooden dowels, which varies with moisture content (MC). This study presents a two-dimensional finite element (FE) model to simulate the bending behaviour of WDCLT panels under varying MC. The model, implemented in Abaqus, combines orthotropic elastic material properties with discrete translational and rotational springs to represent local dowel-lamella interactions. Rotational stiffness is scaled using a calibration factor k eff proportional to MC, which captures the effective degree of mechanical interlock as a function of dowel engagement. The model is validated against experimental bending tests on 5- and 7-layer WDCLT panels conditioned at 8%, 12%, and 15% MC. Numerical predictions match experimental bending stiffness within a relative error of 3%. Calibrated k eff values reveal a strong dependence on both MC and layup configuration, with limited composite action at low MC and enhanced dowel engagement at higher ones. Parametric analyses further quantify the influence of dowel spacing on global stiffness. The proposed modelling approach provides a framework for simulating adhesive-free timber systems and supports the development of performance-based design strategies for WDCLT.