开放型公共场所应急疏散标识优化设计方法研究

为优化设计开放型公共场所的应急疏散标识,根据最短疏散时间、出口匹配原则建立两步优化模型,利用计算机仿真技术及数学优化模型,对开放型公共场所的疏散方案进行优化,合理分配各出口的疏散人数,对区域进行划分并设置相应的疏散标识。以某广场为例,运用上述方法进行疏散标识的优化设计,验证了该方法的可行性和适用性。优化结果表明,各出口的疏散人数分别调整至为282、143、152和424人后,疏散时间较初始状态降低了45.3%。该优化设计方法不仅可为开放型公共场所应急疏散标识的设置提供支持,还可为其他场所制定疏散方案、设置疏散指引标识提供参考。     

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。     

高层建筑火灾初期人员疏散策略的优化分析

通过分析高层建筑火灾条件下的人员安全疏散问题,构建了高层建筑火灾初期的垂直疏散模型,并提出2种疏散策略.策略Ⅰ:电梯停靠层以下全部用楼梯疏散,停靠层及以上楼层用电梯疏散;策略Ⅱ:各楼层人员按不同比例通过电梯进行疏散.然后通过调用随机函数,在一个动态运行模式下求解模型,分析停靠层、楼层人数及电梯疏散人数比例对疏散效果的影响,得到2种策略条件下的近似最优解.分析楼梯、电梯的疏散规律,得出楼层人数、电梯停靠层和电梯疏散人数比例对疏散效果的影响并非单一的线性关系:楼层人数较少时,随楼层的增加,电梯疏散更具优势;楼层人数过多时,电梯、楼梯的疏散效果都不明显,此时需要合理确定通过楼梯、电梯疏散的人数比例才能提高疏散效果.比较2种策略发现,策略Ⅱ疏散时间更短,而策略Ⅰ在现实中的运行能力和可操作性更强.     

基于Pathfinder软件的飞机人员疏散模拟

为弥补飞机适航审定过程中难以大量开展人员疏散演习的缺陷,使用Pathfinder软件对飞机人员疏散模拟开展了研究.根据波音777-200飞机的疏散设施结构,按CCAR-121-R4部要求的标准人员组成,以及实际中的可信不利的人员组成,分5个场景分别进行疏散模拟.根据模拟结果,对影响飞机人员疏散的疏散出口使用率和人员组成进行了分析.结果表明,标准人员组成的疏散模拟结果超过90s,对疏散出口使用率进行优化后,疏散时间才满足90 s的要求.合理的疏散出口使用比例能够减少11％疏散时间.相同人员数量不同人员组成时,疏散时间变化较大.在老年人占80％的疏散场景2中,疏散时间达到107 s;在青少年占50％的疏散场景5中,疏散时间达到96.52 s.通过设置不同人数的疏散场景,并对结果进行曲线拟合,确定了不同人员组成时满足90 s要求的最大允许容纳的人员数量.疏散场景2、3、4和5在满足疏散时间为90 s时飞机所能承载的最大人数分别为310、316、321和329.     

建筑火灾中智能疏散诱导系统对人群疏散的影响

在自制的“黑屋”试验平台上,模拟真实火灾场景,分析了智能疏散诱导系统中安全疏散标识的视觉诱导、声音诱导对人群疏散的影响规律.结果表明:声音诱导与视觉诱导相比,能见度较好时视觉诱导的疏散效率较高;能见度低时声音诱导的疏散效率较高,但安装间距在3 m以内时,视觉诱导的疏散效率较高;疏散之初安全标识的位置对疏散影响明显,随火灾态势的发展和能见度的降低,安全标识的间距对疏散影响显著;正对疏散通道的安全疏散出口利用率最高.     

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.     

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.     

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.     

超市火灾烟气蔓延及人员疏散的模拟研究

针对某大型超市的实际建筑结构以及人员分布情况,利用计算机模拟设定了几种不同情况下的火灾场景,研究了火灾情况下影响人员疏散的因素,并根据烟气运动和人员疏散模拟的结果,对该超市人员疏散楼梯的数量、宽度以及位置分布进行评估.指出了实际超市火灾过程中人员疏散应该注意的一些问题,给出了合理的防火分区划分以及疏散楼梯的分配方式,对超市建筑人员疏散具有一定的指导意义.