The Timber Engineering Notebook series concludes by examining the use of glued-in rods for timber connections. The increased use of manufactured timber, such as glued laminated timber (glulam) and
laminated veneer lumber (LVL), with improved mechanical properties and the ability to produce cross-sections of almost unlimited size, has driven the timber engineering industry to come up with improved connection systems. Glued-in rods and plates have been used in the UK as a method of connecting timber since the 1970s. They offer the possibility of creating concealed connections that are capable of transferring large forces and moments with minimal slip due to their high stiffness.
Glued-in rods differ from traditional timber connections such as bolts and dowels, since they are most frequently bonded into the end-grain of timber, providing opportunities to create alternative connection arrangements and, if detailed correctly, connections that are protected from fire.
Although most commonly used in new construction, glued-in rods have been used for a number of years as a method of repairing decayed and damaged timber in historic buildings, as they allow a high proportion of the original timber to be retained.
Glued-in rods have also been successfully used to improve the compression resistance of timber perpendicular to the grain when bearing is an issue, and to reinforce timber across the grain in areas where splitting can occur, such as the apex of curved arches and close to notches.