隧道结构防火研究综述

随着我国交通隧道建设的飞速发展,隧道的消防安全问题也随之而来,并且受到越来越多的关注;结合国内外近年来在隧道结构被动防火方面的研究进展,总结了隧道火灾的危害性和特点,以及提高隧道衬砌结构耐火性能的措施,为保障隧道的消防安全提供一些参考,并对需进一步深入研究的问题提出建议。     

钢-混凝土组合结构抗火性能研究与应用

钢-混凝土组合结构抗火性能研究是当前的研究热点之一,国内外学者对此展开大量试验研究和理论分析。通过介绍国内外研究者在组合板、组合梁、组合柱等构件以及结构节点和结构体系抗火性能方面研究概况,分析了我国现有防火设计规范的特点以及工程应用情况,指出现有研究的不足,对组合结构抗火研究领域在高温材料热-力耦合本构关系、计算理论、数值火灾试验和设计方法等方面需进一步研究的工作进行了展望。文中指出,建立考虑升降温、多轴应力状态、不同加卸载路径的钢材和混凝土热-力耦合本构关系,建立基于整体性能、考虑升降温全过程的结构抗火分析理论,建立整体结构数值火灾试验方法,提出“三水准”结构抗火设计与灾后结构损伤评估原则以及基于时变可靠度和结构整体性能的组合结构抗火设计方法是钢-混凝土组合结构抗火性能研究的关键科学问题。表2参119     

电力隧道消防设计思考

通过对220kV4回路电力隧道消防系统设计的探讨,系统地阐述了电力隧道消防系统设计的三个部分及应注意的一些问题,从而使电力隧道消防设计更加完善,确保电力隧道消防安全。     

隧道火灾中火羽流特性的数值模拟

利用F luen t软件对隧道火灾中火羽流特性进行了模拟分析,研究了隧道坡度对火羽流的影响,与前人所进行的数值模拟进行了比较,为隧道火灾的研究提供了一种有效的研究手段,为进一步研究隧道火灾临界通风速度奠定了基础。     

Performance assessment of video-based fire detection system in tunnel environment

Compared to tunnels used for other modes of transportation, fire safety design problems in road tunnels are more challenging because of high-speed wind environmental impact. A video-based fire detection system (VFDS) applies inventive mathematical calculations and sophisticated computer models to analyze and tackle real-time video signals statistically and intelligently. VFDS-based temporal flicker modeling of flames and wavelet-based contour modeling approaches are used as weak classifiers. Experimental results have shown that false alarms issued by earlier methods can be significantly reduced by using separate flame and non-flame moving pixels. Whenever the system detects fire or smoke under wind or no wind environment, the VFDS server initiates actions, including visual and audible alarms, alarm messages, and video recording.     

Failure behavior of unbonded bi-directional prestressed concrete panels under RABT fire loading

Although the number of terror-and explosion-related incidents associated with military and terrorist activities is increasing globally, the existing design procedure for civil infrastructures does not consider a protective design for extreme loading scenarios such as blast, impact, and fire loading. Major infrastructure, for example bridges, tunnels, prestressed concrete containment vessels (PCCVs), and liquefied natural gas (LNG) storage tanks are often constructed using prestressed concrete, because it enhances the structural capacity. Concrete is often used as a construction material because of its low thermal conductivity, which makes it a good fire resistant material. However, the fire-resistant behavior of the high-strength concrete (HSC) and prestressing (PS) tendons used in prestressed concrete (PSC) is different than that of ordinary reinforced concrete (RC). Also, there has been limited research comparing PSC to RC under extreme loading conditions. This study presents experimental testing of unbonded bi-directionally prestressed concrete panels with dimensions 1000×1400×300 mm³ that were tested under RABT fire loading to simulate a jet aircraft crash-fire accident. A prestressing force of 430 kN was applied to the PSC specimens using unbonded threaded bars. After a RABT fire test, residual flexural strength tests were performed on the fire-damaged PSC and on RC specimens for comparison. Results of the RABT fire and residual flexural strength tests indicated that the fire-damaged PSC specimens showed severe thermal spalling damage induced by PS relaxation and deterioration of strength/stiffness, respectively. These study results can be used as basic research data for future research in numerical simulation of fire and the design of PSC structures under the fire scenario.     

Fire Evacuation in Underground Transportation Systems: A Review of Accidents and Empirical Research

Previous fire accidents have shown that fires in underground transportation systems, e.g., tunnels and underground stations, can cause many fatalities. It is therefore important in fire safety design to give adequate consideration to all aspects related to evacuation. The main purpose of this paper is to provide guidance to engineers involved in the design of underground transportation systems, and to create a basis for future research in the area. A review of previously reported fire accidents and of empirical research is performed. The review of accidents is based on a theoretical framework, namely four accepted human behaviour theories, which can be used in the fire safety design of underground transportation systems. Factors important for fire evacuation in these types of facilities are also presented, and data related to these factors are summarised. The review reveals many potential solutions to commonly observed evacuation problems, but it also shows that there is room for further future research in the area.     

断面宽度对纵向通风隧道火风压影响研究

针对不同断面宽度隧道中发生火灾时的火风压变化问题,利用Fluent软件模拟隧道内发生火灾的情况,分析隧道宽度对临界风速的影响以及隧道宽度、火源功率和通风速度对火风压的影响。研究表明,火源功率较小时,宽度越小的隧道,临界风速越大;随着火源功率的增大,临界风速之间的差距减小。火风压中火区绕流阻力和热烟摩阻增量会随着风速的增大而相互作用。导致火风压会先随风速的增大而增大,到达一个峰值后会随着风速增大而减小,最后当通风速度增大到临界风速后趋于稳定的数值。随着隧道宽度的增大,通风速率对火风压的影响逐渐减弱。建立不同宽度隧道在不同通风速率和火源功率下的隧道火风压计算公式,为隧道火灾通风设计提供参考。     

火车站火灾自动报警系统设计

摘要现代交通系统变得越来越发达,交通建筑的功能也因为需要满足乘客的各种需求而设计的越来越复杂。交通建筑具有人员密集、发生火灾时疏散难度大等特点,所以火灾自动报警系统的早期预警功能就显得尤为重要。一旦局部发生火灾,火灾探测器能够进行早期预警并进行消防联动,及时将火灾危险消灭于初期阶段,这样才能将社会资源的损失降低到最小并保证交通系统的正常运行。本文对火车站常用的火灾自动报警系统进行阐述,并结合实际设计和使用中遇到的问题,探讨如何能够更好的完成现代交通建筑的火灾自动报警系统设计。     

钢结构抗火研究进展

近二十年来,钢结构的抗火研究一直是建筑安全领域的研究重点,吸引了各国学者的广泛关注和深入研究,并取得了大量的成果。本文简要地介绍了建筑钢结构抗火研究的重要性和意义,对钢结构火灾中的反应研究进行了较为系统的总结,同时指出了其中存在的某些未完善的问题和进一步的研究方向。     

Findings of the International Road Tunnel Fire Detection Research Project

Fire detection systems are essential fire protection elements for road tunnels to detect fires, activate safety systems and direct evacuation and firefighting. However, information on the performance of these systems is limited and guidelines for application of tunnel fire detection systems are not fully developed. The National Research Council of Canada and the Fire Protection Research Foundation, with support of government organizations, industries and private sector organizations, have completed a research project to investigate current fire detection technologies for road tunnel protection. The project included studies on the detection performance of current fire detection technologies with both laboratory and field fire tests combined with computer modelling studies. This paper provides an overview of the findings of the project. Fire detectors, fire scenarios and test protocols used in the test program are described. A summary of the research results of the series of full-scale fire tests conducted in a laboratory tunnel facility and in an operating road tunnel as well as of the computer modelling activities will be reported.     

高速公路火损桥梁安全检测与评估

近年来随着我国高速公路桥梁建设的飞速发展,高速公路桥梁遭受火灾的次数亦在逐渐增多,高速公路特别是国家大动脉承担着繁重的交通运输任务,一旦发生火灾,将直接造成不可估量的经济损失。本文以京港澳高速桥梁遭受火损为例,介绍火损桥梁安全检测与评估方法,为以后类似工程提供借鉴。     

超大断面水平隧道纵向通风临界风速CFD分析

首先介绍了临界风速研究的基本思路及国内外主要研究成果.结合国内某长大公路隧道设计,建立一长300m、水力高度10.64m的水平隧道模型,通过CFD模拟确定超大断面隧道临界风速的影响因子及相应的准则关联式.模拟表明:与火灾热释放速率相比,环境温度的影响可以忽略不计;与Atkinson(模型试验)及Buxton(大尺度试验)相似,临界风速随热释放速率的变化分为两个区域,与低热释放速率时不同,一旦热释放速率超过40MW,临界风速的变化明显趋于缓慢.     

Control of smoke flow in tunnel fires using longitudinal ventilation systems – a study of the critical velocity

The “critical velocity” is the minimum air velocity required to suppress the smoke spreading against the longitudinal ventilation flow during tunnel fire situations. The current techniques for prediction of the values of the critical velocity for various tunnels were mainly based on semi-empirical equations obtained from the Froude number preservation combining with some experimental data. There are a few uncertainties in the current methods of prediction of the critical ventilation velocity. The first is the influence of the fire power on the critical ventilation velocity. The second is the effect of the tunnel geometry on the critical velocity. Both problems lead to the issues of the scaling techniques in tunnel fires. This study addressed these problems by carrying out a series of experimental tests in five model tunnels having the same height but different cross-sectional geometry. Detailed temperature and velocity distributions in the tunnels have been carried out. The experimental results showed that the critical velocity did vary with the tunnel cross-sectional geometry. It was also shown clearly that there are two regimes of variation of critical velocity against fire heat release rate. At low rates of heat release the critical velocity varies as the one-third power of the heat release rate, however at higher rates of heat release, the critical velocity becomes independent of fire heat release rate. Analysis of the distribution of temperature within the fire plumes showed that there were two fire plume distributions at the critical ventilation conditions. The change of the fire plume distribution coincided with the change of the regime in the curves of the critical velocity against fire heat release rate. The study used dimensionless velocity and dimensionless heat release rate with the tunnel hydraulic height (tunnel mean hydraulic diameter) as the characteristic length in the experimental data analysis. It was shown that the experimental data for the five tunnels can be correlated into simple formulae which can be used for scaling. The new scaling techniques are examined by applying the scaling techniques to the present experimental results and three large-scale experimental results available in the public literature. A good agreement has been obtained. This suggests that the scaling techniques can be used with confidence to predict the critical ventilation velocity for larger-scale tunnels in any cross-sectional geometry. Comprehensive CFD simulations have been carried out to examine the flow behaviour inside the tunnels. Validation against the experimental results showed that the CFD gave slightly lower but satisfactory prediction of the flow velocity. However the temperature prediction in the fire region was too high. The findings from the CFD simulations supported the ones from experimental tests.     

含渐缩段卜形分岔合流隧道火灾临界风速研究

为探究“卜”形分岔隧道这一特殊隧道结构对隧道火灾临界风速的影响,运用FDS构建了主路渐缩分岔隧道、主路等宽分岔隧道与直线隧道3种结构的缩尺寸隧道模型,通过数值模拟分析隧道渐缩结构与分岔角度对火灾临界风速的影响。研究表明,对于主路渐缩的分岔隧道,当火源所在位置的局部隧道宽度减小时,所需的临界风量变小。而火源位置确定时,隧道的渐缩结构、分岔角度和分岔结构对临界风速的影响不明显,并提出一种适用于隧道工程渐缩段任意火源位置临界风量的计算公式。对于主路位置的火灾,提出无量纲临界风速与无量纲热释放速率的关系式,与前人直线隧道的变化规律相似,而较高的隧道高度导致临界风速的转折点较大。     

钢结构抗火安全研究现状与发展趋势

火灾引起的高温严重降低建筑钢材的强度和刚度,从而造成钢结构损伤、严重破坏甚至倒塌。20世纪90年代人们开始重视钢结构抗火理论研究,2001年美国“9·11”事件引起了世界各国对钢结构抗火问题的高度关注。结构抗火学科经过几十年的发展,已形成系统的抗火理论和设计方法,文章介绍火灾引起钢结构破坏的原因,论述结构抗火设计原则的发展过程,归纳近年来钢结构抗火研究的重大进展,指出钢结构抗火的重要发展趋势,供有关研究者参考。     

设排烟道隧道的烟气逆流长度与临界风速研究

隧道火灾是运营公路隧道的主要灾害。为有效控制隧道火灾,采用理论分析和数值模拟相结合的方法研究了设排烟道隧道的火灾烟气逆流长度与临界风速。以国内常见的双车道隧道尺寸建立模型,分析了排烟速率和纵向通风速率对烟气逆流长度的影响,提出了临界风速的预测模型。并将其通风效果与常规未设排烟道的纵向通风做了比较。结果表明:未设排烟道时,纵向风速还未达到临界风速时,火灾下游烟气的层化状态就已破坏。设排烟道能及时排出火灾产生的烟气,有利于保持烟气的层化状态,有效改善火灾时的隧道环境,为火灾下游人员的疏散救援提供了有利条件。同时,设置排烟道有利于减小逆流长度和临界风速。随着排烟速率的增大,相应的临界风速呈指数函数递减的特性。     

A probabilistic assessment for classification of bridges against fire hazard

This paper presents the development of a simplified approach for classification of bridges based on fire hazard. Statistical data from recent fires in bridges is utilized to quantify the probable risk of fire in bridges and also probability of fire-induced collapse of structural members in bridges. An importance factor is derived for identifying the vulnerability of bridges to fire hazard. The proposed importance factor, developed using weighted factor approach, takes into account the degree of vulnerability of different bridge components, critical nature of a bridge from traffic functionality point and fire mitigation strategies present in a specific bridge. The proposed importance factor for fire design, which is similar to the one currently used for evaluating wind, and snow loading in buildings, is validated against previous bridge fire incidents. It is shown through this validation that the proposed method for importance factor can be used as a practical tool for identifying critical bridges from the point of fire hazard.     

水平隧道火灾通风纵向临界风速模型

火灾时的烟气控制在隧道防火安全设计中占有很重要的位置,为此通过1/20小尺寸模型实验和全尺寸现场试验对水平隧道火灾通风纵向临界风速进行了研究。根据隧道全尺寸试验和小尺寸实验研究结果,并结合Jae等的小尺寸实验结果以及胡隆华的全尺寸试验和数值模拟结果,建立了水平隧道火灾通风纵向临界风速的预测模型。将模型得到的预测结果跟基于气体火源的实验结果进行对比,结果表明 Wu和Barker通过气体火源小尺寸实验所建立的模型预测值偏低。     

中小型城市高层建筑消防安全管理存在的问题及对策

近年来,高层建筑火灾事故及损失逐年上升,给消防工作提出了新的课题,研究其火灾预防具有现实意义。文章通过对所在辖区高层建筑日常消防安全管理工作的调研,对高层建筑消防安全管理工作存在的问题及火灾预防进行探讨。