Wood and engineered wood product connections using small steel tube fasteners: An experimental study

The work discussed is aimed at identifying combinations of 'wood member' materials and mechanical fasteners capable of creating structural connections that have high initial stiffness, high strength and high ductility. Experimentation shows that the goal can be achieved by joining sawn wood and Engineered Wood Products (EWP) using steel tube fasteners with outside diameters up to 12.7 mm in conjunction with steel plate link elements. Wood members considered are Spruce lumber and Laminated Strand Lumber (LSL), with rectangular cross-sections. In such connections the steel plate link elements are located in slots cut into the ends of wood members so that the plates lie in planes parallel to wide faces of the joined members. Fasteners are placed in tightfitting pre-drilled holes that penetrate both members and link elements. Connection specimens were axially loaded in tension at a loading rate that caused the maximum capacity to be reached in about 0.1 hours. All test specimens exhibited highly ductile failure, as well as good strength and stiffness. Some splitting occurred at failure in specimens with larger sized tube fasteners in Spruce sawn lumber members, reflecting that lumber has inherently low fracture resistance. However, there was no evidence of splitting in specimens with LSL members because it is a highly fracture resistant material. As revealed by the experimentation, it is possible to prevent premature splitting failures in connections that join either sawn wood or EWP provided that tube fasteners are correctly sized.