Enabling the Investigation of Structure Vulnerabilities to Wind- Driven Firebrand Showers in Wildland-Urban Interface (WUI) Fires

Abstract

Wind-driven firebrand showers are a major cause of structural ignition in Wildland-Urban Interface (WUI) fires. Past firebrand investigations have not been able to quantify the vulnerabilities of structures to ignition from firebrand showers, as it is difficult to develop a measurement method to replicate wind-driven firebrand attack on structures that occur in actual WUI fires. To address this problem, research has been undertaken in an intricate area involving the quantification of structure vulnerabilities to wind-driven firebrand showers. This type of firebrand research has never been possible prior to the development of the NIST Firebrand Generator, also referred to as the NIST Dragon. Due the complexity of the WUI fire problem, great strides must be made to recruit the next generation of researchers to fire safety science from diverse backgrounds. This paper closes with a discussion of ongoing workshop activities intended to achieve this, as well as some challenges for future WUI fire research.

Ignition of Wood Fencing Assemblies Exposed to Continuous Wind-Driven Firebrand Showers

“…The NIST Dragon, coupled to a full-scale wind tunnel facility (Building Research Institute's in Japan), has begun to identify vulnerabilities of structures to wind-driven firebrand showers. The interested reader is directed elsewhere for recent comprehensive reviews of the NIST Dragon technology [14,16,18].…”

Exposing Decking Assemblies to Continuous Wind-Driven Firebrand Showers

“…This version of the device is modified from the NIST Dragon [29][30][31][32][33][34] and consists of two parts: the main body and continuous feeding component. The feeding system was connected to the main body and was equipped with two gates to prevent fire spread (described in more detail below).…”

“…BRI maintains one of the only full-scale wind tunnel facilities in the world designed specifically for fire experimentation, the Fire Research Wind Tunnel Facility (FRWTF). Parametric studies have been conducted using the NIST Dragon installed in BRI's FRWTF to expose roofing assemblies, building vents, siding treatments, walls fitted with eaves, and glazing assemblies to wind-driven firebrand showers [29][30][31][32][33][34]. In addition, the dangers of firebrand accumulation in front of structures have been quantified for the first time.…”

The Performance of Concrete Tile and Terracotta Tile Roofing Assemblies Exposed to Wind-Driven Firebrand Showers

“…The tile gaps are on the order of 3 mm. Penetration of the tile gaps was not a surprise as prior work by Manzello et al [11] observed firebrands penetrating a 1 mm wire mesh. The terracotta tile roofing assembly constructed of profiled tiles (no interlocking) performed similarly to both types of concrete tiles used; namely firebrands were observed to penetrate the tiles and melt the sarking.…”

“…In these experiments, the sarking material was observed to melt, yet full penetration of the sarking material by glowing firebrands was not observed. This is important because penetration by burning firebrands could ignite materials below the sarking, such as fine fuels found in attic spaces, as shown by Manzello et al [11]. In addition, it was also not possible to conduct experiments for wind speeds larger than 10 m/s.…”