Chord Shielding Effect in Steel Trusses When Exposed to a Localized Fire

Stadia and other gathering places are often built using long spans of lightweight truss systems that allow for unobstructed views. Due to these large open spaces and the structure often being built from steel trusses, fires within these spaces are often localized and the residual strengths of the damaged areas need to be immediately evaluated. These buildings are made to accommodate large events, such as concerts and sporting events, so when a fire occurs, the need for the evacuation of the entire space can be costly. One such example occurred at a sports event in 2022, when a speaker in the rafters caught on fire. The entire stadium was evacuated, resulting in a large financial loss as all tickets were refunded and broadcast suspended. The uncertainty in the residual condition of the structural system after a fire means there is a risk to the safety of occupants, and it takes time to assess the damage that occurred, both to the flame impinged truss and any adjoining system which may have taken additional load during the fire. It is therefore important to understand how a localized fire could impact common structural systems in stadiums. This would help address life safety concerns, while also lowering any financial impacts. This research herein aims to record the temperature distribution, using thermocouples, within a generic OWSJ when it is exposed to a known localized heat source. The potential for any heat shielding effect of the bottom chords of the OWSJ to the upper chords will be investigated using a 30-min methanol pool fire. This will provide the required raw data to validate modelling tools which can be used to analyze stadium structures during localized fire events, especially regarding their residual conditions afterwards. Guidance could therefore be generated using the results of this study to help practitioners determine post-fire conditions and the structures’ resiliency.