How changing fire management policies affect fire seasonality and livelihoods

There is a long history of fire management in African savannas, but knowledge of historical and current use of fire is scarce in savanna-woodland biomes. This study explores past and present fire management practices and perceptions of the Khwe (former hunter-gatherers) and Mbukushu (agropastoralists) communities as well as government and non-government stakeholders in Bwabwata National Park in north-east Namibia. Semi-structured interviews and focus groups were used in combination with satellite data (from 2000 to 2015), to investigate historical and current fire management dynamics. Results show that political dynamics in the region disrupted traditional fire practices, specifically a policy of fire suppression was initiated by colonial governments in 1888 and maintained during independence until 2005. Both the Khwe and Mbukushu communities use early season (i.e. between April and July) fires for diverse interrelated historical and current livelihood activities, and park management for managing late season fires. The Mbukushu community also use late season burns to prepare land for crops. In this study, we use a pyrogeographic framework to understand the human dimension of fires. This study reveals how today’s fire management practices and policies, specifically the resurgence of early season burning are entrenched in the past. Understanding and acknowledging the social and cultural dynamics of fire, alongside participatory stakeholder engagement is critical for managing fires in the future.Electronic supplementary materialThe online version of this article (10.1007/s13280-020-01351-7) contains supplementary material, which is available to authorized users.     

Factors related to injury of shiftworking fire fighters in the Northeastern United States

Fire fighters, who provide society with an essential and life-saving service, are subjected to the effects of shiftwork and to the demands (physical and mental) and dangers of their profession, all of which can contribute to injuries. To identify factors involved in injuries to fire fighters, the timing, frequency, types, and places of occurrence of injuries sustained by fire fighters in three different municipal fire departments were examined. Data was obtained from analysis of Workers' Compensation forms. The most frequent injuries involved inhalation of hazardous materials and lacerations. Ninety-two percent of the injuries occurred at the fire scene, and their causes were related to fire fighting duties, such as rescue, extinguishment and overhaul. Although only 54% of fire alarms nationwide occurred from 12:00 to 16:00 and from 18:00 to 24:00 (42% of a 24 hour day), 68% of the injuries sustained by the fire fighters studied occurred during these time periods. Per alarm, at meal time or on the night shift fire fighters were more likely to be injured. Serious injuries were more prevalent at standardly accepted meal-times. The timing of the highest frequencies of injuries suggests that, due to the shiftwork nature of firefighting, both disruption of eating patterns and fatigue increase the risk of work-related injury to fire fighters. By understanding the contribution of factors, especially human ones, such as altered metabolism (due to disruption) and fatigue (due to time elapsed since awakening, alteration/disruption of sleep-wake pattern, or hypoglycaemia), interventions can be developed, which should decrease the incidence of injuries to fire fighters.     

Numerical investigation into dynamic responses of RC columns subjected for fire and blast

Structures may be exposed to fire and blast due to accidents (i.e. explosion of flammable gas in industrial structures) or terrorist attacks during the service life. Performances of RC structures subjected to extreme conditions of fire and blast, thus, have drawn much attention from academia. In this paper, the coupling effect of high temperature and high strain rate in concrete was firstly studied based on the experimental data to improve the damage plasticity concrete model in ABAQUS. Secondly, the transient heat transfer effects in different fire scenarios and following fire resistances of RC columns with constant axial forces were numerically investigated on the basis of the improved concrete model, which are validated by the corresponding test data, and the residual axial loading capacity of RC columns was quantitatively calculated. By incorporating the different merits of implicit algorithm applied to heat transfer analyses and explicit algorithm usually used in blast analyses, a numerical approach to analyze the responses of RC columns subjected to the coupling loadings of fire and blast was finally developed. Mid-span displacements and damage of the RC columns subjected to fire and explosions were quantitatively calculated and discussed. The proposed approach was demonstrated to be effective in predicting the responses of RC structures subjected to coupling loadings of fire and blast.     

基于化学反应动力学机理的中等尺寸甲烷湍流扩散火焰的数值模拟

通过代码修改,在大涡模拟(LES)中嵌入气相化学反应速率、组分热力学性质和输运特性三大机理文件,严格意义上实现甲烷燃烧的四步简化机理与火灾动力学模拟软件(FDS)的成功对接。燃烧模型采用针对多组分燃料的涡耗散概念(EDC)模型,模拟0.3m直径的甲烷湍流扩散火焰,并分别与基于无限快反应速率的总包单步和两步化学反应预测结果对比。分析预测结果可知:四步机理能够很好的适应FDS框架,其模拟结果具有可靠性,时均温度、速度和主要反应物的预测结果高度一致;机理导入后可以预测CO2、H2O以及中间产物CO和H2的浓度,更合理地描述了火灾中气相产物的产生与输运过程。不同反应机制下主产物CO2和H2O浓度对比结果理想,在高温反应区内存在一定的差异,在高温反应区外呈现出高度的一致性。     

机械式立体停车库中巷道防火分隔效果研究

使用火灾CFD模拟软件Fire Dynamic Simulator(FDS)建立某机械式立体停车库的火灾动力学模型,研究停车库内巷道的防火分隔作用和巷道顶部的排烟窗对烟气的控制情况。确定了此机械立体停车库的火灾发生概率为0.00786起/年,并调研了车库汽车火灾的热释放速率模型。根据模拟结果,当巷道一侧一辆车着火后,巷道另一侧车辆受到的辐射热流密度为0.6kW/m2~2.0kW/m2,不会引燃巷道另一侧车辆,利用巷道空间作为防火分隔措施是可行的。巷道顶部自然排烟百叶对于控制烟气有着显著作用,在顶层距地面10m高度处,500s时仅起火停车单元及其对面停车单元能见度低于10m,而未开设排烟窗时整个车库能见度均降至10m以下,局部区域在2m以下。     

广西苍梧马尾松林和大叶栎林的火行为比较

马尾松(Pinus massoniana)是中国南方大面积造林的树种,也是抗火能力最弱的树种。研究了广西苍梧11龄马尾松用材林和4龄大叶栎萌芽林在正常冬季和干旱夏季情景下的火行为,用behaveplus计算了火线强度、蔓延速度、树冠火可能性等参数。结果表明,两种林分在干旱夏季的火行为高于在正常冬季的火行为。无论是在正常冬季还是在干旱夏季,都没有出现马尾松可燃物模型的火行为一致高于大叶栎可燃物模型的情况;天气、地形、可燃物床结构对可燃物含水率有很大影响,而含水率是火行为的决定因素。虽然大叶栎被划分为难燃树种,大叶栎萌芽林的火行为高于成年大叶栎乔木林,苍梧大叶栎萌芽林在极端干旱的夏季情景有被火把点燃的可能性。如果将大叶栎萌芽林作为防火林带使用,需要经常清除林下枯枝落叶,割除黑莎草,减少细小可燃物。     

On the mechanism of a BLEVE occurrence due to fire engulfment of tanks with overheated liquids

The BLEVE (boiling liquid expanding vapor explosion) effect that involves the formation of a fireball occurs at the engulfment by fire of a tank with a highly flammable liquid or a liquid gas. Heating of the tank causes elevation of the liquid phase temperature and pressure inside the tank. A partial rupture of the dry tank walls is possible, with the formation of a rarefaction wave propagating into the liquid phase. An evaporation wave moves after the rarefaction wave and cause a rapid increase of pressure, exceeding the initial pressure before depressurization. Rapid violent destruction of the tank occurs. The mechanism of a BLEVE initiation is considered using Van der Waals isotherms. The following criterion for the possibility of a BLEVE was formulated. If the final state is located on an unstable part of the Van der Waals isotherm, a BLEVE takes place. Limiting values of the temperatures for overheating of certain highly flammable liquids and liquid gases (propane, n-butane, n-pentane, isopentane) were calculated using the proposed method, and were found to be in good agreement with experimental data available in the literature.     

通用森林火险级系统

根据火烧试验,研究出来一套包括火险等级、火行为与火烈度等的完整系统.用公式R_0=aT bV ch-D计算日燃烧指标R_0(米/分)。此方法曾于1991年5月试用在小兴安岭伊春林区得出满意的结果。     

轨道交通车辆段火灾探测系统对比分析

作为轨道交通网中重要的组成部分,轨道交通车辆段如果发生火灾将直接影响着轨道列车的运行。因此,适用于轨道交通车辆段的火灾探测器对保障车辆段的消防安全至关重要。结合城市轨道交通车辆段结构及环境特点,选取了管路采样吸气式和双鉴成像式线性光束式等两种火灾探测器开展了实体火灾实验。实验对比分析了两种火灾探测器在不同火源工况下的响应情况并综合分析了两种火灾探测器的响应性能,从而为实际工程中轨道交通车辆段火灾探测器的选型及布置提供参考。     

突然进风对室内火灾影响的实验研究

以工业酒精为燃料，在一房间与走廊相联的模型中，研究了封闭燃烧一定时间后，突然进风对室内火灾的影响。分别在走廊进风。起火室进风等情况下，观察了燃烧状况的变化，测量了典型截面的温度分布，并对一些现象出现的原因作了分析。指出这种突然进风，可在短时间、一定范围内降低温度，但主要效果是促进燃烧。当室内有明火源时还会引发烟气回燃，致使其中的温度急剧升高。