Impact of Firefighting Sprays on the Fire Performance of Structural Steel Members

Abstract

The feasibility of coupled computational fluid dynamics (CFD) and finite element (FE) simulations to aid the planning of fire intervention tactics and the effectiveness of structural cooling during firefighting were investigated. Water sprays, generated using fire monitors, were characterized using bucket tests and the results were used for calibrating the CFD spray model. The cooling ability of the sprays was measured experimentally by applying them onto a fire exposed steel beam. The experimental results showed that water application produces a sudden drop in steel temperatures and after 10–15 s, no significant further reduction in temperature was observed. The CFD-FE coupling was performed using the adiabatic surface temperature method, extended here to include the cooling by water droplets. The coupled CFD-FE model was validated using the experimental data and applied to simulate the intervention to a developing warehouse fire, showing how an attempt to cool the structure reduces the temperatures but does not stall the fire-spread. In fact, the intervention -induced vapor generation was found to enhance the flow of hot gases and accelerate the fire-spread if the water resources are inadequate. Thermal and stress analyses of the cooled and uncooled truss beams were performed, showing how the spray cooling halted the truss mid-span deformation.

Behavior of fin-plate connection of a composite beam subjected to different fire scenarios

“…During the heating and cooling cycles, if the beams are unloaded from plastic range to elastic range, the accumulation of the residual deformations can activate the catenary actions at temperatures below 400 °C. The similar fluctuations of the structural responses of the steel truss beams inside the warehouse with and without fire interventions were also reported in [6] and [7] because of the heating and cooling cycles during the fire spreading and backward travelling and during the cooling by insufficient water sprays. In these studies, the connections between steel beams and columns were modelled either as pinned connections or fixed connections without considering connection details.…”