Applying timber-insulation mixed ceiling strategy in CFD simulation of large open-plan compartment with non-uniform fuel load

Abstract

Engineered timber products are increasingly popular in modern architecture due to their sustainability, ease of installation, and visual appeal. However, the combustibility of exposed timber elements presents significant fire safety challenges, particularly in modern large open-plan compartments. Previous experiments demonstrate rapid fire spread once timber ceilings ignite, highlighting the urgent need for effective fire mitigation strategies. Using a CFD fire model validated against a full-scale compartment fire test, the performance of the previous study on the proposed design strategy for the ceiling involving a mixed surface of timber and non-combustible insulation strips, complemented by a reinforced concrete upper layer, for mitigating fire spread has been demonstrated. Given that real-world fuel distributions are often non-uniform, this research specifically further investigates the effectiveness of the mixed ceiling strategy under non-uniform fuel scenarios, which may pose higher fire risks than conventional uniform arrangements. Results confirm that the mixed ceiling effectively delays fire growth and maintains localized burning for extended periods, especially when coupled with optimized fuel spacing and enhanced ventilation conditions. Parametric analyses further reveal that increasing the proportion of insulation relative to timber enhances fire mitigation, even under extreme fire scenarios. The flexible design principles inherent to the mixed ceiling strategy thus provide substantial structural and safety benefits, demonstrating reliable performance under challenging fire scenarios and supporting performance-based fire safety design.