Timber Joints with Multiple Glued-in Steel Rods

Timber joints with glued-in rods constitute a viable solution for numerous applications as they exhibit advantages, e.g., the formation of very stiff connections, high fire resistance, and improved aesthetics. Most previous research has focused on testing single rod joints to evaluate the influence of parameters on structural performance; in practice, however, multiple steel rods are required to transfer the loads from one structural component to the next. The lack of design guidance related to the performance of multiple glued-in rods hinders the widespread application of this joint type. This paper describes experimental investigations on joints composed of glued-in steel rods in glue-laminated timber. The influence of the anchorage length was studied to establish performance benchmarks; then joints with multiple rods (two, three, and four rods with the spacing between rods varied) were manufactured and tested under uniaxial quasi-static tension loading. The results showed that for joints using multiple mild steel 12.7 mm glued-in rods, a ductile failure can consistently be attained if: i) the anchorage length of the rod is longer than 10 times the diameter; and ii) the spacing between rods is five times the rod diameter. The results contribute toward a better understanding of the performance on timber joints with multiple glued-in rods.