Statistical Determination of Ignition Frequency of Structural Fires in Different Premises in Finland

Ignition frequencies and ignition frequencies per floor area were determined for different building categories in Finland as total groups and as a function of the floor area of the building. These frequencies are needed as input for risk analysis using performance based fire safety design. It was found that differences between building categories or location within country were so small that a universal curve for the whole country could be determined. For ignition frequency per floor area for small buildings a strong dependence on size is observed, but it remains approximately constant for larger buildings. Additionally periodical variations of ignition frequency of buildings by month and week of year, day of week, and time of day were determined. Historical review of the development of ignition frequency models was made. Some evaluation on the generality of the results was made based on the theoretical models.     

A note on estimation of intensities of fire ignitions with incomplete data

Occurrences of fire ignitions in a given region during a specified period of time are modelled as outcomes of a Poisson point process. The ignition frequency is considered a function of the total floor area of the building. Parameter estimates and their uncertainties are computed. Different criteria for model selection are used. The proposed methodology is specifically useful in the case with small data sets or lack of information about the population at risk.     

Aspects of stochastic modeling for structural firesafety

A brief review is presented of methods for stochastic modeling of fires of sufficient severity to threaten the, structural safety of buildings. Information is provided on the rate of fire occurrences according to the floor area at risk for the major occupancy types. National Bureau of Standards Center for Fire Research     

Modelling the evacuation of a high-rise office building in Istanbul

The use of advanced computer models for the analysis of evacuation problems in buildings under fire conditions or terrorist attacks has become an increasingly important research area. Until recently, most safety considerations regarding the evacuation of a building are taken on the basis of some deterministic rules prescribed in fire codes. However, these rules and design principles may not be sufficient to explain the complex interaction between a vast numbers of variables affecting the evacuation process. Also, the characteristics of a fire can differ from building to building and occupants can demonstrate distinctly different behavioural patterns and physiological characteristics. As a result, potential weaknesses, particular to the investigated building, can go unnoticed which, in turn, may result in disastrous consequences during an emergency. The study concentrates on two issues: firstly, what methodology should be pursued to accurately model an evacuation problem and the derivation and extent of parameters needed to fully utilise the potentials of the advanced computer models, in this case, the buildingEXODUS; the second issue is an investigation of the evacuation behaviour in a high-rise office building in Istanbul. It is found that exit knowledge and the preferences of occupants can severely slow down the evacuation process. Fires closer to the ground floor increase the death toll significantly. Failure in the activation of the sprinkler system or the absence of the system altogether can have disastrous effects on the loss of life.     

大型公共建筑火灾研究与探讨

大型公共建筑的突出特点是内部空间大、容纳人数多、疏散困难 ,因此成为火灾事故防范的重点对象。针对大型公共建筑防火设计存在的诸多问题 ,借鉴国内外的研究经验 ,探讨我国大型公共建筑性能化防火设计的研究方向     

Capacity reduction and fire load factors for LRFD of steel columns exposed to fire

Capacity reduction and fire load factors corresponding to the load and resistance factor design (LRFD) format are developed for steel columns exposed to fire. A sample deterministic framework to determine fire and steel temperatures and the capacity of steel columns is adopted for this analysis to structure the methodology. A specific number of parameters that affect the structural response, including the fire load, ratio of floor area to the total area of the fire compartment, opening factor, thermal absorptivity of compartment boundaries, thickness, density and thermal conductivity of insulation, dead load, and live load are taken as random variables. Mechanical and sectional properties of steel (e.g., yield strength, cross-sectional area, etc.), are also considered to be random variables. The effect of active fire protection systems (e.g., sprinklers, smoke and heat detectors, fire brigade, etc.), in reducing the probability of occurrence of a severe fire is included. Given the choice of framework and based on detailed reliability analyses, it is shown that the capacity reduction and fire load factors should vary depending on the presence of active fire protection systems in a building.     

火灾下钢结构楼板的薄膜作用

通过对真实火灾中的足尺火灾试验和观察显示，合组合楼板和承载钢梁的建筑物的结构承载力比现行杭大设计方法的建议值高出许多。因此规范中规定所有承载钢梁都要添加被动防火保护是不必要的。现行设计方法和实际结构性能之间产生这种差异是由于设计方法中忽略了楼板的薄膜作用。本根据国外有关资料给出了几种简单计算方法，允许在钢结构杭大设计中考虑楼板的薄膜作用。从而可以更精确地评估火灾下建筑物的真实承载能力，在给定的耐火时间内能减少相当数量钢梁的防火保护。     

The timing of vegetation fire occurrence in a human landscape

Vegetation fires in urban and peri-urban (human) landscapes damage property and infrastructure, threaten lives and incur considerable suppression costs. This study investigated the timing of fires burning in vegetation within and around the city of Perth, Western Australia. The timing of fires from 16 different cause types were investigated at hourly, daily, monthly and annual scales, and using fire danger indices and fuel moisture. Ignitions from most causes were shown to have hourly and monthly profiles that reflect fire danger and fuel availability. Some causes with low heat outputs, such as cigarettes and sparks from cutting and welding, were more sensitive to fire danger and fuel availability than others. Causes related to arson and recreational activities, such as camp fires, were more likely to occur on weekends and public holidays. Arson prevention measures appear to have reduced the incidence of deliberately lit fires, and may have reduced the number of fires occurring on days of total fire ban, although these days have much higher rates of ignition than other days. High profile fire events also increase public awareness and reduce ignition rates. Lessons learned from analyses of fire occurrence can help fire agencies more effectively apply prevention and mitigation programs.     

Data-driven probabilistic post-earthquake fire ignition model for a community

Fire following earthquake (FFE), a cascading multi-hazard event, can cause major social and economical losses in a community. In this paper, two existing post-earthquake fire ignition models that are implemented in Geographic Information System (GIS) based platforms, Hazus and MAEViz/Ergo, are reviewed. The two platforms and their FFE modules have been studied for suitability in community resiliency evaluations. Based on the shortcomings in the existing literature, a new post-earthquake fire ignition model is proposed using historical FFE data and a probabilistic formulation. The procedure to create the database for the model using GIS-based tools is explained. The proposed model provides the probability of ignition at both census tract scale and individual buildings, and can be used to identify areas of a community with high risk of fire ignitions after an earthquake. The model also provides a breakdown of ignitions in different building types. Finally, the model is implemented in MAEViz/Ergo to demonstrate its application in a GIS-based software.     

住宅建筑防火层数确定的若干问题

本文通过"住建规"、"建规"、"高规"对住宅建筑层数折算不同规定的分析,仔细探讨了底层与顶部跃层扣减以及"临界层"的问题。希望通过对问题的探讨,扩展大家的视野以及解决疑难问题的思路。     

The modeling of fire spread in buildings by Bayesian network

Fire spread modeling is very important to fire safety engineering and to insurance industries involved in fire risk–cost analysis of buildings. In this paper, the Bayesian network is introduced. The directed acyclic graph of a fire spread model is presented. When the fire ignition location is known, the fire spread model based on the Bayesian network from the compartment of fire origin to another compartment can be built, and the probability of fire spread can be calculated by making use of the joint probability distribution of the Bayesian network. A specific application for an office building is presented for a case without sprinkler and one with sprinkler installed.     

低辐射强度下古建筑木构件材料的燃烧特性

为研究古建筑木构件材料在火灾下的燃烧特性,使用锥型量热仪对古木材试样的点燃时间、临界辐射强度、热释放速率、燃烧气体中CO2体积分数等燃烧特性进行试验研究。试验发现3种不同厚度试样的临界辐射强度分别为8.81,9.40,10.55 kW/m2。试样厚度增加会使古木材点燃时间延长,临界辐射强度增大,材料的热释放速率所形成的双峰值曲线的峰值降低。燃烧气体中CO2体积分数曲线与热释放速率所绘制出的曲线的形态一致,同一厚度的试样在不同辐射强度下其燃烧特性呈现出显著区别。与新木材相关燃烧特性参数对比,劣化后的古木材临界热辐射强度降低、点燃时间减小,5 min内平均热释放速率较高。研究表明,古建筑木构件材料燃烧特性有显著变化,可为古建筑火灾研究提供参考。     

Assessment of fire reaction and fire resistance of Guadua angustifolia kunth bamboo

The main challenge for construction industry today is sustainability. Bamboo has properties that make it sustainable, but its fire behavior remains unknown. This paper presents an exploratory research on fire behavior of Guadua angustifolia kunth (a.k.) bamboo. Fire reaction was assessed through critical heat flux for ignition and flame spread while fire resistance through charring rate and strength variation with temperature. Fire reaction fall within standard limits used for structural woods, while fire resistance results are higher than that of plywood. Based on these preliminary results, Guadua a.k. would be adequate as structural and indoor finishing building material.     

外墙窗户面积及位置对建筑外立面火蔓延的影响

搭建20层的全尺寸办公建筑三维模型,通过设置不同窗户面积、窗户位置研究外窗对建筑外立面竖向火蔓延的影响。研究发现窗户面积较大时,火灾竖向蔓延速率更快,室内温度升高更快,采用大的窗墙比更容易加快火灾在建筑外立面的竖向蔓延。在竖直位置上,随着窗户上移,各楼层的引燃时间均增加。     

CFD modelling of the effect of fire source geometry and location on smoke flow multiplicity

Understanding solution multiplicity of smoke flow at the same building configuration and ambient conditions is important for managing smoke flows and human evacuation in buildings. One of the known examples with solution multiplicity is in a simple single-compartment building on fire under an opposing wind. The occurrence of multiple solutions of smoke flow is induced by competing wind and thermal buoyancy forces. Under a given and moderate wind, the critical buoyancy flux ratio for the existence of smoke flow multiplicity, which is a ratio between defined parameters representing buoyancy force and wind pressure, is related to building height and opening area, as shown using a zone model. Computational fluid dynamics (CFD) simulations were used here to evaluate whether the behaviour of smoke flow multiplicity was affected by the geometry and location of the fire source(s). Our simulation results were in good agreement with previous macroscopic analysis results. A floor fire source can produce the largest smoke flow rate in the buoyancy-dominated flow regime among the tested cases while two corner sources can produce the smallest smoke flow rate. A floor source had a relatively large smoke flow rate in the wind-dominated flow regime while a point source had relatively small smoke flow rate. Moreover, a larger critical buoyancy flux ratio and a larger range of fire power in which smoke flow multiplicity existed were found for a floor fire source than for other sources. Switching of smoke flow solutions in building fires was found to depend on the initial conditions and the magnitude of flow perturbations.     

An engineering tool to calculate heat release rates of multiple objects in underground structures

Simple theoretical calculations of the overall heat release rate (HRR) of multiple objects have been carried out. The results were compared to fire experiments in a model tunnel using wood cribs placed at equal distances from each other. Three different methods are presented which are based on physical relations for fire spread between the wood cribs. The first method uses a critical heat flux as ignition criteria while the other two methods use an ignition temperature. The method using the critical heat flux as ignition criteria shows very good agreement with the corresponding experimental results used. The two methods using the ignition temperature as ignition criteria did not agree well with the corresponding experimental results. The prerequisites, that the methods should be kept relatively simple to be of practical use and that the burning objects should not necessarily have to be of uniform composition, were fulfilled.     

Mass occurrence of Penicillium corylophilum in crawl spaces, south Sweden

Buildings with crawl space foundations are looked upon as high-risk constructions with respect to mould growth, especially on the blind floor. This mould growth can be extensive and cover several square meters of the blind floor with potential health risks as a consequence.Mould occurrence and mould species diversity were investigated in a large small-house area in the south of Sweden, comprising 212 buildings. The crawl spaces were inspected and samples from the blind floor were taken. The relative humidity was measured and reached 80–100% for several consecutive months. Subsets of the samples were cultured and the fungi isolated were further analyzed by sequencing of the Internal Transcribed Spacer (ITS) region of nuclear ribosomal Deoxyribo Nucleic Acid (DNA). The results were compared with results from other, relevant studies and confirm that Penicillium corylophilum is the completely dominating mould species in crawl spaces. The occurrences could not be explained as accidental since the extensive occurrence in many dwellings had developed over several years.     

高层建筑电梯楼梯协同疏散的仿真实验研究

近年来高层建筑逐渐增多,但高层建筑普遍存在逃生线路长,火灾严重性大的问题。为了缩短高层建筑在消防疏散中的疏散时间,降低高层建筑火灾发生后的事故严重程度,利用疏散软件Pathfinder分析了高层建筑中使用电梯楼梯协同疏散的可行性。结果表明:高层建筑电梯可以作为协同疏散的辅助工具,增加一部电梯比单纯增加电梯最大运行速度要更加有效;设置每层电梯都使用总人数的固定比例进行疏散的时候,楼梯资源不易被充分利用;当设置n层及n层以上每层总人数的不同比例使用电梯进行向下疏散,存在最佳疏散楼层N11及最佳疏散比例20%,最后一个通过电梯疏散完毕与最后一个通过楼梯疏散完毕的人员仅相差2.7s,此方法可以为相关高层建筑火灾疏散策略的决策提供一定的参考依据。实验结果说明了电梯疏散的教育和培训很重要,在高层建筑中合理使用电梯进行疏散可以很大程度减少总疏散时长。     

Burning behavior of sedan passenger cars

Four full-scale fire experiments using 4-door sedan passenger cars were carried out. The cars were ignited either at the splashguard of the right rear wheel or at the left front seat in the passenger compartment with a gasoline spill. The temperature inside the burning car and the mass loss rate were measured. The burning of the 4-door sedan was composed of three compartmental fires: the engine compartment, the passenger compartment, and the rear part inclusive of the fuel. In the experiments where ignition was initiated at the splashguard, the flame spread in the following order: to the rear part of the car, to the passenger compartment, and to the engine compartment. Breakage of the window glass markedly affected the spread of fire into the passenger compartment. The quantity of gasoline in the fuel tank also affected the speed of spread of the fire, because the gasoline ignited at an early stage of the fire. In the experiment where ignition was initiated in the passenger compartment, the fire gained force after the windshield was broken entirely. The flame spread in the following order: to the passenger compartment, to the engine compartment, and to the rear part of the car. The temperature within the passenger compartment peaked at 1000 °C. The heat release rate (HRR) curves showed several peaks depending on the burning of the three compartments. The HRR increased markedly when the fire spread to several different parts of the car at the same time. The HHR peaked at 3 MW when the passenger compartment and fuel (gasoline) burned simultaneously. The measured HRR curves were characterized by superposition of a Boltzmann curve and a Gaussian curve in order to obtain a model, which allowed us to make a more precise prediction of the fire spread probability from a burning car to nearby structures. The HRRs of burning cars were described by the sum of HRR from each compartment.