Behaviour of bolted steel splice connections under fire

Steel connections play a crucial role in steel frames subjected to loading both under ambient and elevated temperature conditions. In fact, the susceptibility of a steel structure to failure or collapse especially when exposed to fire is largely contingent on the robustness of the connections, hence, the structural behaviour of connections constitutes a central research theme which has continued to attract significant attention.
The results of an experimental and a numerical study on the performance of bolted web-flange splice (BWFS) connections in fire are presented herein. A total of eight connections were tested in a furnace using ISO 834 heating curve and observations on their ductility under elevated temperatures are reported. The specimens were subjected to both moment and shear loads under 3-point and 4-point loading arrangements. The parameters investigated in the tests were connection load ratio, loading configuration, and bolt size. The observed failure modes and ultimate strengths obtained for the connections from the experimental data were compared with strength predictions from EC3 equations and the latter were found to be conservative for all the cases investigated. A finite element model was developed and validated with results from the experiment to enable the effect of bolt grade on the connection behaviour to be studied. Results in the form of temperature versus rotation (T-θ) curves are presented and failure modes are discussed to provide useful insights on the performance of these connections in fire.