Design of Glued-in-rods connections in timber structures

Timber structures in glulam are booming in recent years. It has led to the development of high-performance connections, like glued-in-rods (GiR). Glued-in-rods are threaded rods inserted into boreholes with glue. They offer aesthetic advantages, high performance and stiffness. Lack of knowledge about this connection, whose design is not governed by the Eurocode, considerably limits their use. This study presents experimental testing on glulam beam-to-column connections using glued-in-rods and a traditional connection (metal clamp). Two configurations of GiR connection are tested, one with 2 rods, and one with 4 rods. Experimental tests show that glued-in-rods connections have greater rotational stiffness than the traditional connection. The observed failure modes of the connections were the yielding rods by tensile force. It was also concluded that capacity appears to be a function of the number of rods: doubling the number of rods doubles the capacity of the connection (rods on the same axis). The same applies to rotational stiffness. Comparison of experimental results with model predictions showed good agreement, with a deviation under 15% for the maximum tension experienced in the rods.