Experimental evaluation and theoretical prediction of single hardwood dowel connections in softwood and hardwood

Abstract

This study presents a comprehensive evaluation of single wooden dowel double-shear joints tested under compression loading parallel to the grain. Tasmanian Oak (a premium Australian native hardwood) was used as the dowel material, while Spotted Gum (a high-density native hardwood) and Radiata Pine (the most widely planted softwood in Australia) were used as the timber members. Wooden dowel timber-to-timber connections (WDTCs) exhibited initial elastic embedment of the dowel, followed by mixed-mode failure involving tensile bending and tensile shear. These failure modes are not accounted for in the yield limit equations of the National Design Specification (NDS) or Eurocode 5, resulting in inaccurate predictions of stiffness and load capacity for WDTCs. There is limited research on mechanics-based modelling of WDTC stiffness and capacity. In this study, several theoretical models were refined, adapted, or newly developed to predict joint stiffness, yield load, and maximum load capacity. These include beam-on-elastic-foundation models, spring-in-series models, post-test deformation–based models, embedment stiffness-based model and Johnson theory–based models for both uniform and non-uniform stress distributions. All these models are assessed against the current WDTC test data. The capacities were also compared with the new Eurocode 5 proposed yield-limit equation for WDTCs. Complementary tests, including embedment of timber with steel and wooden dowels, isolated dowel embedment, and dowel bending, were conducted to improve understanding of WDTCs behaviour and to provide input parameters for the theoretical models. The refined and newly developed mechanics-based models can be applied either independently or in conjunction with NDS models for WDTCs design.