Evaluation of the Behavior of Composite Double Web-Angle Connections at Ambient Temperature and in a Fire Situation

Steel–concrete composite connections play a crucial role in ensuring the transfer of forces between steel and concrete structural elements. Additionally, the safety of structures during fire incidents has gained significant attention worldwide. This study focuses on investigating the behavior of composite double web-angle connections under ambient temperature and fire conditions using numerical analysis. After adjusting the numerical models, a parametric analysis was conducted. The results revealed that the composite double web-angle connections exhibited semi-rigid behavior at ambient temperature. Moreover, the fire event altered the failure mechanism of the connections. A negative reinforcement rate of 0.75% resulted in the maximum stiffness at room temperature and the biggest variance in rotational capacity under a fire condition, according to the parametric analysis. Furthermore, parameters such as slab type, steel–concrete interaction, bending moment direction, and steel and concrete strength all had a substantial impact on the behavior of the connections under both ambient and fire circumstances. This paper also includes practical formulae for determining the moment resistance and starting stiffness at ambient temperature, as well as the lowered stiffness during a fire and the cumulative variance in rotational capacity for composite double web-angle connections.