Manzello Samuel L, Suzuki Sayaka
Fire Research Division, National Institute of Standards and Technology (NIST), Gaithersburg, MD USA.
Large Fire Laboratory, National Research Institute of Fire and Disaster (NRIFD), Chofu, Tokyo, Japan.
Fire Saf J. 2017 Sep;92:122-131. doi: 10.1016/j.firesaf.2017.05.019. Epub 2017 Jun 27.
Wildland-Urban Interface (WUI) fires have become a problem of great concern across multiple continents. An important mechanism of structure ignition in WUI fires and urban fires is the production of firebrands. During WUI fires, decking assemblies have been observed to be an ignition vulnerability based on post-fire damage surveys conducted by NIST and elsewhere. The authors have conducted scoping experiments and demonstrated the dangers of the dynamic process of continual, wind-driven firebrand showers landing on decking assemblies for wind speeds of 6 m/s. In this study, eight full-scale experiments were conducted with wood decking assemblies under a wind speed of 8 m/s. The basis for these new investigations was twofold: observe possible vulnerabilities of wood decking assemblies to continuous, wind-driven firebrands at higher wind speed as firebrand accumulation patterns were expected to be influenced by wind speed, and examine if wall ignition occurred due to the burning decking assembly. To this end, sections of wood decking assemblies (1.2 m by 1.2 m) were constructed and attached to a reentrant corner assembly. The deck/reentrant corner assembly was then exposed to continuous, wind-driven firebrand bombardment generated by a full-scale Continuous Feed Firebrand Generator installed in the Fire Research Wind Tunnel Facility (FRWTF) at the Building Research Institute (BRI) in Japan. The mass of firebrands required for flaming ignitions under a wind speed of 8 m/s was considerably less compared with those under a wind speed of 6 m/s. This result is postulated to be due to higher firebrand surface temperatures as the wind speed was increased. For the decking assembly to wall ignition studies, the interface between the decking assembly and the wall appeared to be a weak point; this is not addressed in the current test methods.
城乡交错带（WUI）火灾已成为多个大洲极为关注的问题。WUI火灾和城市火灾中建筑起火的一个重要机制是产生火旋风。在WUI火灾期间，根据美国国家标准与技术研究院（NIST）及其他机构进行的火灾后损伤调查，已观察到地板组件存在着火隐患。作者进行了范围界定实验，并证明了持续的、风驱动的火旋风阵雨以6米/秒的风速落在地板组件上这一动态过程的危险性。在本研究中，在8米/秒的风速下对木质地板组件进行了8次全尺寸实验。这些新研究的依据有两个：观察木质地板组件在更高风速下对持续、风驱动的火旋风可能存在的脆弱性，因为预计火旋风堆积模式会受风速影响；检查燃烧的地板组件是否会导致墙壁着火。为此，建造了木质地板组件部分（1.2米×1.2米）并将其连接到一个凹角组件上。然后将地板/凹角组件暴露于由安装在日本建筑研究所（BRI）火灾研究风洞设施（FRWTF）中的全尺寸连续进料火旋风发生器产生的持续、风驱动的火旋风轰击之下。与6米/秒风速下相比，8米/秒风速下引发明火所需的火旋风质量要少得多。据推测，这一结果是由于风速增加时火旋风表面温度更高。对于地板组件到墙壁着火的研究，地板组件与墙壁之间的界面似乎是一个薄弱点；当前的测试方法未涉及这一点。
