The impact of travelling fires on structural integrity in large compartments – Findings from test 1

Large-scale compartment travelling fire tests were carried out at FireSERT, Ulster University, by the authors to study their behaviour and their impact on the surrounding structure. This article provides detailed temperature data recorded during Test 1 (fuel controlled with open boundary conditions) and explores how the positioning of the travelling fires affect the temperatures of both the compartment gas and the surrounding structural elements. The parts of the compartment and the steel structure discussed in this article are all within the fuel bed and parallel to the direction of the travelling fire along the centre of the test compartment. It is found that the travelling fires yield complex and non-uniform temperatures within the compartment and their positioning has a significant impact on the recorded temperatures. It was observed that the differences in the recorded gas temperatures for areas near and further from the travelling fire band can be around 900 °C (especially at lower levels) at certain instants during the test. The same differences for columns and beams are around 600 °C and 300 °C respectively at some instants during the tests. Unlike the current assumptions for small compartments, the gas temperatures recorded along the length of large compartments are highly transient during travelling fires. Similar observations were made for the recorded temperatures in the steel beams and columns. Temperatures in the upper parts of the columns rise uniformly at earlier stages of the fire test while the lower parts experience high sharp temperatures when the travelling fire band engulfs the columns. In case of beams, the increase and decrease in temperatures is steady, however, the temperatures recorded in the bottom flange are higher than those recorded in the top flange. The findings of this research reflect the learnings from accidental fires which are different to the conventional approaches used in the fire design. These findings will improve our understanding of the fire dynamics related to travelling fires, their impact on building safety and will provide better direction for future research on travelling fires.