Characterizing the Performance of Adhesive Used in Glued-In Rod Timber Connections at Elevated Temperatures

A glued-in rod, which combines timber, a metal rod, and structural adhesive, is a type of connection whose fire performance is complicated to define since the rod depends on the adhesive's thermomechanical properties. The objective of this study was to characterize the fire performance of adhesives used in glued-in rods. A total of five structural adhesives were tested: three epoxies and two polyurethanes. The tests performed consisted of applying an axial load to the glued-in rods after heating the connection to a target temperature. Load-slip curves were generated for each sample to determine their behavior at different temperatures. The results show that a reduction of up to 70% can occur in the initial stiffness of the glued-in rod when the temperature at the bond line exceeds the glass transition temperature of the adhesive determined by a dynamic mechanical analysis. This research helps to determine the guidelines for the fire design of glued-in rods and related testing and ultimately leading to a design method for providing fire-resistance to connections made of glued-in rods.