Influence of glue rheology and joint thickness on the strength of bonded-in rods

The maximum pull-out strength of bonded-in rods was used for investigating the relationship between the joint geometry and the rheology of the structural adhesive. Tests with a brittle and a ductile glue type, both formulated with epoxy resins, showed that the glue rheology has a strong influence on the joint behaviour. The joint thickness is also an important parameter, having a good correlation with pull-out strength and with the fracture typology. Wood density and moisture content had a very low influence on strength, in these test conditions. A modification of the Eurocode 5 equation was developed, allowing an improved use of the adhesive properties for a safer design. Results suggest that a standardised test method for bonded-in rods would be very helpful for the determination of basic joint properties such as the maximum joint thickness and the glue strength parameter that were used in the modified design equation.