Fire resistance of steel shear connections

• The fire performance of single plate and angle connections is significantly different.
• Angle connections are flexible and ductile compared to single plate connections.
• Angle connections are more robust under fire conditions with adequate bolt strength.
• Bolts of angle connections experience significant tensile force due to prying action.

The strength and stability of connections in a floor system is an integral part of a building structure. A connection is subjected to large compressive and tensile forces during heating and cooling phase of a fire, respectively. However, shear connections are only designed for gravity loads that produce shear, and there is a lack of knowledge in their behavior at elevated temperatures. In this study, the fire response of the single plate, the single angle and the double angle shear connections is investigated in a subassembly under a natural fire by using three-dimensional finite element models with surface-based contact interactions. The results show that different types of shear connections do not affect the global behavior of the subassembly during the heating phase of the fire, where the fire response is generally governed by beam local buckling near the connection. However; the connections behave significantly different during the cooling phase. The angle connections provide more ductility and flexibility compared to the single plate connection but the high-strength bolts experience large tensile forces due to prying action.