Hugrún María Friðriksdóttir’s scientific contributions

Tolerance gaps in wood connections are unavoidable, for reasons of constructability and the effects of natural shrinkage in timber elements with changing moisture content. During a fire, these gaps may lead to a substantial heat transfer to the metal connectors that are considered heat protected being embedded by the wooden components of the connection. Aluminium connectors are popular due to their ease of production and assembly, but they are particularly vulnerable to elevated temperatures. This study investigates the effects of tolerance gaps on the fire performance of aluminium connectors in beam-to-column/wall shear connections. Reduced-scale experiments were designed to study the temperature evolution of aluminium connectors during standard fire exposure for 1 mm and 6 mm tolerance gaps, as well the mitigation effects of additional intumescent fire protection in a 6 mm tolerance gap connection. For the 6 mm gap, the temperature of the connector increased much faster, reaching 286 ± 36°C after 80 min, at which time the connector with a 1 mm gap had only reached 97 ± 1°C. The addition of intumescent protection in a 6 mm gap case led to lower temperatures in the connection, in comparison to an equivalent tolerance gap without protection. Subsequently, two additional loaded fire tests were performed, for 6 mm and 22 mm tolerance gaps without fire protection, to investigate the critical failure mode of the connectors. In these cases, the failure occurred in the connectors at 87 min and 32 min, respectively, when their average temperatures reached approximately 315°C. This study demonstrates the critical influence of gap size on the fire performance of aluminium-wood joints.

Tolerance gaps or slips in wood connections are unavoidable, for reasons of constructability and the effects of natural shrinkage in timber elements with changing moisture content. During a fire, these gaps may lead to increased heat transfer through the connection. Aluminium connectors are becoming more popular due to their high malleability and availability, but they are particularly vulnerable to elevated temperatures. Thus, the objective of this study is to investigate the effect of tolerance gaps on the fire performance of aluminium connectors in beam-to-column/wall shear connections. An experimental campaign was designed to study the temperature evolution of the aluminium connectors during standard fire exposure for 1 mm and 6 mm tolerance gaps, as well the mitigation effects of additional intumescent fire protection in a 6 mm tolerance gap connection. The results showed a clear and consistent impact of the connection gap size on the temperature evolution of the aluminium connectors. For the larger 6 mm gap, the temperature of the connector increased much faster, reaching 286 ± 36 °C after 80 minutes, at which time the connector with a 1 mm gap had only reached 97 ± 1 °C. The addition of intumescent protection in a 6 mm gap case led to lower temperatures in the connection after 40 minutes of fire exposure, in comparison to an equivalent tolerance gap without fire protection. This study shows that tolerance gaps can lead to a significant reduction in the capacity of aluminium connectors, but this may be mitigated with additional fire protection.