New developments in data regression methods for the characterization of thermal stratification due to fire

The study deals with the data regression methods used for validating zone code modeling in comparison with experimental fire tests. These methods aim at determining both the temperatures of upper and lower zones and the interface location calculated from experimental vertical temperature profiles. A new data regression method is proposed to improve the determination of upper and lower temperatures and position of the interface. This new method merges both the thermal stratifications showing constant temperature in the upper layer as often encountered for well ventilated fire (approach of Quintiere et al. [4]) and those showing constant gradient as often observed for fire in closed and forced ventilated compartment (approach of Audouin et al. [8], [9]). These two latter existing methods and the new former one are then applied to large scale fire tests experiments performed in IRSN facilities. The major outcomes indicate that the most appropriate regression method depends on the basic shapes of the experimental vertical temperature profiles. The interface height is the most sensitive variable to the choice of the regression methods. Indeed, discrepancy higher than 100% can be found concerning this last variable. In contrast, the temperature of lower zone appears to be the less sensible variable. The discrepancy on the upper temperature is found also significant in some cases. From these investigations, guidelines are proposed to improve the data regression process needed for validating zone codes and are supported by a thorough analysis of these three data regression methods using experimental data from large-scale fire tests.     

电缆隧道火灾分析及计算机模拟

对电缆隧道火灾进行了分析,应用火灾动力学模拟软件FDS对电缆隧道火灾过程进行了计算机模拟,并对其火灾发展过程和防火保护措施进行了初步讨论。结果表明,电缆隧道为高火灾危险场所,在火灾情况下,隧道内维持较高温度,电缆将持续燃烧,火灾具有发展迅速、结构可能严重损伤、烟气量大、有害气体浓度高、扑救困难等特点,对其火灾危害性应引起足够重视。     

Numerical study of the behaviour of a surface fire propagating through a firebreak built in a Mediterranean shrub layer

The efficiency of a firebreak, built in a shrubland has been studied numerically using a multiphase physical model. The physical mechanisms governing the propagation of the surface fire and the consequences upon the temperature signal and the radiative heat flux received by a target located at 1 m above the ground level, have been firstly studied before positioning the firebreak. The role played by the flame and the recirculation of hot gases to the ignition of unburned fuel (especially the dry grass) ahead of the fire front have been clearly identified. Four values of the firebreak width L_C (ranged between 5 and 20 m) and 3 values of wind velocities (ranged between 1 and 8 m/s) have been tested. The simulations show that above a threshold value of this parameter, even if a small amount of the fuel located on the opposite side of the firebreak was ignited, the released energy was not sufficient to sustain the propagation of the surface fire after crossing the firebreak.     

浅谈数据挖掘技术在消防系统中的应用

介绍了数据挖掘技术的概念及功能，并结合消防的现状讨论了数据挖掘在消防领域中的应用，构造了一个消防系统数据挖掘模型。     

响应面法在结构可靠度分析中的应用研究

响应面法可以应用于大型复杂结构隐式极限状态方程的可靠性分析,然而至今可靠度响应面法的计算精度仍是未完全得以解决的问题.本文分析了响应面法计算结构可靠度的实质,指出了已有可靠度响应面法研究中存在的认识误区,并揭示了可靠度响应面法计算误差的真正原因.在此基础上,提出了改进响应面法用以解决传统响应面法收敛失败和计算误差大的问...     

基于改进响应面技术的火灾下混凝土结构可靠度分析

采用热力耦合分析火灾中的建筑结构计算工作量比较大,而要进一步获得各种不确定性因素影响下的结构可靠度就更为困难.针对上述问题,综合热力耦合分析技术、改进响应面技术和结构可靠度分析方法,提出了一种更为高效的火灾过程中结构可靠度分析的计算方法.其基本过程是采用均匀试验方法组织一定次数的热力耦合分析获得结构构件温度和内力分布,在此基础上回归出分析参数和构件温度、内力之间的响应面,结合响应面和Monte Carlo法得到各构件的可靠度.结合某混凝土建筑分析了该建筑主要构件在火灾作用下的可靠度.     

Numerical simulation of surface forest fire in Brazilian Amazon

This paper investigates fire spread through surface fuels of the Brazilian Amazon by using a three-dimensional, fully transient, physics-based computer simulation approach. Computer simulations are obtained through the solution to governing equations of fluid dynamics, combustion, heat transfer and thermal degradation of the vegetative fuel. Surface fuel fires composed mostly of dead leaves and twigs were numerically simulated and the calculated rate of spread was compared to findings from field observations. The importance of air humidity, vegetation temperature, moisture content, surface to volume ratio and bulk density was evaluated through the variation of each one individually in numerical simulation runs. Conclusions show that in the range of parameter variation considered, the most important parameters are the vegetation moisture, surface area to volume ratio, and bulk density. The vegetation initial temperature and air humidity, in the range of variation studied, did not influence the fire rate of spread. The numerical simulations also showed that the radiation process is very important and directly affects the fire rate of spread. Convection is less important because of the absence of external wind. The model is able to capture the main effects of a surface forest fire typical of the Amazon, and can be used as a numerical tool for studying such fires.     

Sensitivity of fire size to fireline construction rates in a simulation model

An initial attack model was sensitive to changes in production rate of suppression forces, as shown by changes in final fire size.The adequacy of fireline construction rates used in fire planning models has been questioned. A fire containment model was tested over a range of suppression force productivities to show the effect on final fire size. The percentage of fires that escaped was sensitive to the productivity of line-building units. The degree of sensitivity depended on the severity of environmental conditions. Final fire size was most affected by fireline construction rates under the most severe environmental conditions tested. Using distributions of production rates from weighted averages of the results produced final fire sizes similar to those obtained using point estimates in the simulation model. Planners may be able to use graphs like those presented, in place of iterations of a fire containment model. Reference: Eric L. Smith, Sensitivity of Fire Size to Fireline Construction Rates in a Simulation Model,Fire Technology, Vol. 22, No. 2, May 1986, p. 136.     

数据挖掘在实体火灾实验中的应用研究

为实现高效、迅速地完成实体火灾实验,充分发挥数据潜力,重点研究数据挖掘与深度网络在自动喷水灭火系统实体火灾实验中的应用。通过选取合适的算法,逐步确定模型中的各参数,建立了有效的数据挖掘模型。该模型可以减少风险,提高实验质量,缩短实验周期,形成更具智慧的实体实验决策。     

中庭火灾模型数值与实验研究

结合火灾相似模型实验对中庭火灾数值模型进行了比较，其中采用的燃烧子模型充分考虑了火源燃烧及蔓延过程对于烟气流动的影响。利用PHOENICS软件开发的应用程序计算表明，大空间建筑火灾数值模拟采用燃烧子模型和辐射换热模型，可以更好地反映出火源释热率的变化情况。计算结果与实验数据比较，定性合理。     

几种金属面夹芯板的耐火性能测试

用垂直构件耐火试验炉研究不同厚度的金属面岩棉夹芯板、EPS夹芯板、聚氨酯夹芯板、酚醛夹芯板的耐火性能.用岩棉与EPS、岩棉与聚氨酯进行组合进行耐火性能测试,100 mm厚的岩棉—EPS夹芯板、岩棉—聚氨酯的耐火极限分别达到85、90 min,较大提高了EPS夹芯板和聚氨酯夹芯板的耐火性能.     

某办公大楼中庭的消防安全性能化分析

提出了中庭采用自然排烟所带来的消防问题。采用计算流体力学(CFD)方法对烟气在中庭中的传播进行了模拟分析。通过对模拟结果的分析，提出了有关加强中庭消防安全措施的建议。     

燃料载荷和含水率对平坡地表火蔓延影响实验研究

燃料载荷和含水率是森林火灾中地表火蔓延的重要影响因素.选取香樟叶和云南松松针作为研究对象,开展了不同燃料载荷和含水率条件下平坡地表火蔓延实验.研究结果表明:同一燃料载荷下,随含水率增大,火焰长度、火蔓延速率、火线强度和辐射热流减小,滞留时间增大;同一含水率下,燃料载荷增大,火焰长度、火蔓延速率、火线强度、辐射热流和滞留...     

华南地区森林地表可燃物火蔓延速度特性的实验研究

摘 要：华南地区植被丰富,人类活动频繁,一旦发生森林火灾,后果严重。为探究华南地区森林地表可燃物种类和燃料床特性对火蔓延速度的影响规律,给扑救森林火灾提供参考数据,通过实地采样与室内燃料床火蔓延速度测量实验,定量分析了森林地表可燃物火蔓延速度特性。实验结果表明,桉树叶燃料床在5种燃料床中蔓延速度最快,加上其在该地区的种植情况,具有较高的火灾危险性。得到了桉树叶燃料床特性对火蔓延速度影响的规律,发现含水率开始增加阶段,蔓延速度衰减很少,含水率超过14%后,蔓延速度快速衰减,到18%后蔓延速度衰减再次减少;蔓延速度与厚度成幂函数关系,厚度增加使蔓延速度增加;堆积密度、宽度对火蔓延速度影响不大。     

基于PMC指数模型的消防安全管理政策评价

为全面、直观考查消防安全管理政策的相关特征,从政策属性、政策内容与政策执行三个维度构建了基于PMC指数模型的消防安全管理政策评价指标体系.利用PMC指数得分与PMC曲面对指导意见类、管理规定类、加深执行力度类、专项行动类等多份典型消防安全管理政策开展了评价分析,厘清了不同类型消防安全管理政策的主要特征,并从突出领域特色...     

Reliability analysis of laterally loaded piles using response surface methods

Response surface methods have been applied to the reliability analysis of laterally loaded piles. Beam elements and a series of discrete springs are used to model the pile–soil system. The pile head displacement and the maximum bending moment in the piles are used as the performance criteria in this study. It is shown in the illustrative example that the CDF and PDF curves of the pile head displacement and the maximum bending moment in the pile obtained from the proposed methods are in good agreement with Monte Carlo simulation. The failure probabilities of the pile under specified performance criteria, the probabilistic responses of the pile-soil system, and the effect of pile-soil parameters to the failure probability of the pile are also studied.     

Large eddy simulation of compartment fire with solid combustibles

For properly describing practical building fire processes with solid combustibles, the pyrolysis kinetics model of solid combustibles and the large eddy simulation (LES) approach are applied to the simulation of the thermal decomposition of the polyurethane foam (PUF) slab and the space fire spread in a compartment. The instantaneous variations of the heat release rate of the PUF slab, the smoke temperature, and the smoke interface height with time are obtained under different ventilation conditions. They are in agreement with the measured data. The ventilation conditions have distinct effects on the interactions between the pyrolysis of the PUF slab and the space fire spread. Influenced by the space fire spread, the heat flux on the top plane of the PUF slab exhibits a non-uniform distribution. The PUF slab is consumed in an asymmetric manner.     

大跨度斜拉桥扁平钢箱梁的多尺度可靠度分析研究

以润扬大桥斜拉桥为分析对象,提出了扁平钢箱梁结构的多尺度可靠度分析方法。采用子结构方法将扁平钢箱梁整体结构尺度模型和局部构件尺度模型相互衔接,在此基础上采用改进响应面法分析了扁平钢箱梁结构的静力可靠度。分析结果表明：①采用改进响应面法能有效地解决传统响应面法存在的收敛失败和计算误差大的缺点;②采用钢箱梁多尺度模型可以较准确地计算斜拉桥在活荷载作用下的静力可靠指标;③钢箱梁活荷载的分布方式和斜拉桥的几何非线性对斜拉桥静力可靠度具有较大的影响;④采用钢箱梁多尺度模型,可以较真实地研究钢箱梁局部构件损伤对斜拉桥静力可靠度的影响。钢箱梁局部构件损伤对斜拉桥静力可靠指标的影响程度要明显大于对斜拉桥静力特性的影响。因此,在斜拉桥钢箱梁的可靠度设计与状态评估中需要计入结构多尺度效应的影响。     

基于NURBS的建筑曲面建模技术研究

针对建筑结构中复杂曲面的高精度建模要求 ,提出采用NURBS建模方法建立建筑结构中复杂曲面的几何模型 ,通过建立模型 ,为进行复杂建筑结构的强度分析仿真和进行城市规划的视景仿真提供高精度的几何模型数据