Experimental Investigation of Composite Beams with Shear Connections Subjected to Fire Loading

This paper presents the results from experimental investigations focused on the thermal and structural behavior of composite beams with shear connections subjected to fire conditions. Five partial composite beams with flat, lightweight concrete slabs were designed according to current U.S. codes and standards. Vertical loading was applied to the composite beams, and the surfaces of the steel and concrete were heated using high-temperature ceramic radiant heaters. Variations in the loading and heating protocol provided insight into the mechanical response and failure modes of composite beams and connections. There was an overall reduction in the composite beam load-carrying capacity due to heating, both at elevated temperatures as well as postfire ambient conditions. Concrete compression failure occurred at moderate steel temperatures (350–500°C) combined with overloading. In cases where service level loading was applied, the composite beams and connections sustained the loading and heating up to steel temperatures of 700°C. However, the shear-tab connection fractured during cooling, which highlights the importance of considering both the heating and cooling phases of a fire.