Wind impacts on fire spread and structural failure during bushfire in complex terrain

Severe bushfires occur as single or concurrent fires under conditions of high fuel loads (vegetation), weather, and relief (topography). Bushfires have a range of ignition sources and are characterised by both spatial and temporal elements which are difficult to predict. While bushfire may occur in grasslands, heaths (scrublands), woodlands or forests, major events associated with forest fires in rugged terrain give rise to the greatest concern largely due to the higher fuel loads and characteristic canopy fires associated with forests. The inaccessibility of more rugged and remote areas makes control difficult, especially where these are associated with multiple lightning ignitions and strong winds. Fires which are difficult to control and with major fire runs, often in inaccessible areas, can develop into raging catastrophic infernos causing widespread property damages and loss of lives. While most work has focused on the principal agents of bush fire attack, that is embers, radiant heat and flame contact, little has been developed to consider the effects of fire generated winds. Construction practice, as applied through the Building Code of Australia, provides some opportunities for improved building resilience in the face of bushfire attack, however, wind loading does not form part of this assessment process. This paper seeks to provide a model for understanding the phenomena of fire-induced winds and suggests a framework for developing improved practice for the protection of buildings from fire-induced wind storms.