Fundamental advances for the fire safety of tall timber structures including the fire decay phase (FIReSafeTimber)

Urban densification, sustainability drivers and technological advances foster the development of high-rise structures using bio-based materials like engineered wood products. Their main worldwide barrier relates to fire safety. Although a natural fire has a decay phase, structural capacity is traditionally assessed according to a standard fire curve: an unrealistic ever-increasing thermal exposure with time, conceived as worst-case design scenario. This results in inadequate assessment for timber, often disqualifying it as potential material. Also, the decay phase, deemed less onerous due to its lower temperatures, is generally omitted from structural calculations. However, for structural performance it is of crucial importance for timber. Unlike traditional non-combustible construction materials, wood loses its mechanical properties at relatively low temperatures. Thus, the precise interaction between fire and structure needs to be understood because the temperature propagation through the load-bearing timber can unexpectedly lead to structural collapse, even after a fire seems extinguished. Current regulations fail to consider this hazardous issue and available literature on the matter is limited. Fundamental technical issues still need to be resolved and pertain to the nature of the fire dynamics and the resulting deterioration of the engineered timber mechanical properties. In FIReSafeTimber computational models are built to simulate the thermal exposure to structural elements for various fire dynamics conditions (e.g., fuel and compartment characteristics). Bench-scale and full-scale fire tests are conducted on loaded timber structural elements with varying fire decay phase. FIReSafeTimber will formulate a novel constitutive model to predict the heat transfer and the structural capacity of timber elements and will develop performance-based methodologies for the fire-safe design of timber structural systems that include the effects of the fire decay phase.