Measurement of the Thermal Parameters of Composite Materials During Fire Tests with Quantitative Infrared Imaging

A fire resistance test, as performed on plates of carbon fibre reinforced polymer composites, is conceptually analogous to a step heating, and can be modelled by the one-dimensional heat equation. Thus modelled, the plate operates as a linear system with an impulse response function that relates temperatures at the front face (the one exposed to fire) and the rear face, and depends on two parameters, namely thermal diffusivity (\(\alpha \)) and effective Biot number (Bi). Taking as input the time evolution of temperature at the front face, the output of the model for each (\(\alpha \), Bi) couple is a predicted temperature for the rear side of the plate. At each point of the plate, \(\alpha \) and Bi can be retrieved by fitting the predicted temperature to the experimental one. These parameters are good quantitative indicators of thermal damage, and therefore its measurement has a particular interest to understand degradation processes associated with fire action. To perform their retrieval as described, temperature measurement for both faces of the plate during the experiment are made with a specifically developed infrared imaging system, composed by two synchronized infrared cameras that image both sides of the sample during the fire test and provide surface temperature maps, spatially co-registered and with the flame effects filtered out. Applying the fitting procedure described to these temperature maps makes possible, for the first time, to measure \(\alpha \) and Bi in situ during the fire test. The value of \(\alpha \) obtained by this procedure (varying from \(\approx 0.5 \times 10^{-7} \, \mathrm{m}^{2} \, \mathrm{s}^{-1}\) in the region most affected by fire, to \(\approx 7 \times 10^{-7} \, \mathrm{m}^{2} \, \mathrm{s}^{-1}\) near sample edges) has been compared to those measured after the test, on samples at room temperature, with the classical flash method. A good general agreement has been found, with differences that can be attributed to the temperature dependence of diffusivity. From this comparison a critical temperature of \(T = 450^{\circ }\)C has been identified, that separates two different regimes, probably related to different degradation states, with slopes of \(-\,1.5 \times 10^{-9} \, \mathrm{m}^{2} \, \mathrm{s}^{-1} \, \mathrm{K}^{-1}\) for \(T<450^{\circ }\)C and \(3 \times 10^{-10} \, \mathrm{m}^{2} \, \mathrm{s}^{-1} \, \mathrm{K}^{-1}\) for \(T>450^{\circ }\)C.     

A Review on Structural Fire Tests of Two-Way Composite Floors

Fire Technology - The utilisation of composite floor systems in modern construction allows for building large floor areas with efficient use of material and labour. The efficiency of this flooring...     

复合材料的A级防火测试研究

按照GB 8624—2006研究了复合材料进行A级防火性能测试的方法,并结合一些实例分析了同一种测试样品可能进行的各种测试项目组合。分析表明,对于任何一种复合材料,要达到A级防火性能,都可能会有3～4种测试方案组合。只有加深对标准的理解,才能正确地评定产品的燃烧性能,从而有针对性地制定出提高产品燃烧性能的方案。     

分光光度计及红外光谱仪在建筑材料检测领域的应用

介绍了分光光度计和红外光谱仪在常规领域的检测应用,重点对分光光度计和红外光谱仪在建筑材料的化学分析、玻璃陶瓷和隔热涂料等方面的检测应用进行了分析和探讨。     

火灾混凝土建筑物红外热像鉴定技术与案例

根据红外热像检测原理,采用红外热像仪检测火灾损伤的钢筋混凝土结构,分析其受火温度、强度损失及损伤深度,并综合评价其损伤等级。现场检测实践表明,钢筋混凝土结构火灾损伤的红外热像检测与评估,可快速获取比较全面翔实的建筑物火灾损伤资料,从而为修复加固工程提供科学可靠的依据。     

钢-混凝土组合楼板实用抗火设计方法

利用钢-混凝土组合楼盖抗火性能非线性有限元分析程序对不同荷载大小、不同压型钢板厚度、不同配筋的压型钢板-混凝土组合楼板进行了抗火性能分析,找出了火灾影响下组合楼板结构性能的因素,给出了计算组合楼板耐火时间的拟合公式,得到了一些适用于压型钢板-混凝土组合楼板抗火设计的结论和建议。     

两种坡缕石基复合调湿材料的热湿性能测定与比较

鉴于调湿材料的热湿物性决定着其热湿传递行为,研制了2种新型坡缕石基复合调湿材料——坡缕石基亚麻纤维材料(FP)和坡缕石基木质纤维材料(WFP),全面测量了这2种复合调湿材料的水蒸气渗透系数、等温吸附曲线和湿扩散率等关系到其吸放湿能力和热湿传递特征的物性参数,探究了材料厚度和相对湿度上下限对复合调湿材料湿缓冲值的影响.结果表明：材料越厚,相对湿度区间越高,复合调湿材料的吸放湿能力就越强;厚度为2.5 cm的FP和WFP的湿缓冲值分别达到2.83、3.11 g/(m²·%).     

聚乙二醇/水泥基复合相变材料的制备与表征

基于水化-结晶法,以聚乙二醇为相变材料,硫铝酸盐水泥的水化产物为基体,利用聚乙二醇的水溶性和硫铝酸盐水泥的水硬性制备了一种高聚乙二醇含量的水泥基复合相变材料（CPCMs）,研究了其微观结构、化学兼容性、晶体结构、相变特性、热稳定性及降温效果.结果表明：聚乙二醇能够均匀地分散在硫铝酸盐水泥水化产物构成的多孔网络结构中,负载情况良好;聚乙二醇与硫铝酸盐水泥水化产物的化学兼容性良好,二者没有发生化学反应;CPCMs在250℃以下具有良好的热稳定性,具备用于相变储热沥青路面的温度条件;当聚乙二醇质量分数为36.36%时,CPCMs的相变焓高达62.48 J/g,与对照组硫铝酸盐水泥相比,其表面温度降低了7.3℃.     

组合节点端板连接节点高温性能的研究现状与前景

对高温下钢一混凝土梁柱端板连接节点的研究现状做了较全面的综述。近年来随着组合结构在土木工程中不断地推广应用,高温下构件、节点、结构体系的耐火性能成为组合结构抗火研究的重点。一些高温试验、有限元软件数值模拟的建立、理论模型成为近几年来的主要研究手段。但在现有的研究中,对一些影响参数和节点处于各种应力状态下的受力性能仍然没有做合适的考虑,这些因素将导致理论存在一定的误差,因此有必要进行更为深入的理论研究。     

A Fire Safety Assessment System for Existing Buildings

In Hong Kong which is characterized by its tall, reinforced-concrete buildings with multiple owners, most of the high-rise buildings constructed before the mid-1970s are dilapidated. In order to address this problem, the Hong Kong Government intends to introduce mandatory safety assurance requirements with its so-called Building Safety Inspection Scheme, under which building owners would be required to appoint building professionals to assess the safety level of their buildings and to recommend appropriate corrective actions. In order to ensure uniform standards and easy administration, the Hong Kong Government intends to publish assessment guidelines. One of the major safety aspects the guidelines will addresses is fire safety, since, over the past few years, several large, tragic fires have occurred in the city's high-rises. This article proposes a fuzzy fire safety assessment approach based on fire risk ranking techniques that may form part of the safety evaluation tool for existing buildings. The basic principles of the system are briefly described, and its implementation is outlined.     

红外热成像技术在工程建设中的应用

红外热成像技术作为一门无损检测技术具有轻便、快速、直观、非接触、大面积、远距离探测等特点和优点。本文讨论了影响红外技术测试精度的主要因素及相应解决办法,介绍了其在工程建设领域的若干应用,取得了较好的效果。     

Fluid-Structure Simulations of Composite Material Response for Fire Environments

The focus of this effort is to develop models and numerical methods for coupled simulations of composite material response in fire environments. This research has comprised of two main activities. The first is the development of a thermo-mechanical damage model for composite materials subject to high temperature environments. The damaged composite is expressed as two regions of non-charred and charred materials. Homogenization methods are used to formulate the damaged material in terms of volume fractions of the composite fiber, resin, char and gas. Results are presented for a clamped beam case with comparison to experimental data for a glass-phenolic composite. Overall good agreement is observed between model predictions and measurements of temperature and pressure. The clamped beam is observed to undergo an interesting bifurcation for which the beam bows away from the applied heating load due to thermal expansion, but then later in time, bows towards the applied heat load after sufficient char is formed. The second research activity is on the development of fluid-structure coupling algorithms for simulating the coupled response of 2D composite structures and the local flow environment. Results show that the spatial distribution of material decomposition is sensitive to the local flow environment from the fire that, in turn, is defined by the structure geometry. Near the material surface enhanced heat transfer to the material surface is observed from the near-wall flame that is established by the resin off-gases. These observations highlight the importance in considering the coupled response of both the material response and the flow field for assessing the performance of composite structures for fire environments.     

火中聚合物基复合板结构的完整性设计

对火中聚合物基复合板在热和机械荷载组合下的受压承载力进行探讨。其典型案例是受火后横向温差下船体结构中板的状态。研究聚焦在横向温差和压缩机械荷载下的破坏模式。即由中心轴引起的弯曲、挠度和没有机械荷载的热变形。提出破坏模型的温度场和机械场并从设计角度对细节问题进行了探讨。对于设定的耐火时间,给出了设计机械荷载下的设计图;与此相对应,对于给定的机械荷载,设计了耐火时间。与传统的造船钢板不同,随温度变化的横向温差的设计过程包含多维破坏机理。     

钢-混凝土组合梁抗火性能研究综述

随着钢-混凝土组合梁的广泛应用,组合梁的抗火性能和设计方法越来越引起人们的重视。目前关于钢-混凝土组合梁的抗火性能研究文献还不多。对国内外钢-混凝土组合梁的抗火性能试验和理论研究以及高温下栓钉的受力性能研究进行了文献综述,指出了目前研究中存在的问题和不足。此外,还对国内外常用的几个规范中关于钢-混凝土组合梁抗火设计方法和理论进行了分析和总结,用一个算例计算了组合梁的临界温度并进行了对比。最后对未来的研究趋势进行了展望。研究工作可为开展钢-混凝土组合梁抗火性能研究和进行组合梁抗火设计提供参考。     

A Fire Safety Evaluation System for Prioritizing Fire Improvements in Old High-rise Buildings in Hong Kong

Fire safety in old high-rise buildings is of great concern to the general public as a result of several big fires occurred over the past 10 years. A fire safety evaluation system is essential for building engineers to quantify the fire safety level, to identify the measures to be improved and to schedule the corresponding improvements. Together with a scoring system with weighting factors derived for local buildings, this paper proposes a universal fire safety evaluation (FSE) checklist for fire safety level quantification and improvements prioritization in old high-rise buildings. In a survey, the fire safety levels of 122 old high-rise buildings in Hong Kong were quantified using the scoring system. The survey results showed that only less than 5% of the inspected samples reached the standard required for life safety. The FSE checklist was then applied to prioritize the improvement works of 10 selected buildings with the lowest scores.     

红外热像技术在房屋渗漏检测中的应用

采用红外热像技术对某酒店卫生间的渗漏进行了分析并鉴定,为维修方案的确定提供了技术支持。该红外热像法通过检测建筑物表面的辐射温度,根据建筑物的红外热成像照片特征判定防水缺陷,可在不破坏或较少破坏装修的情况下准确找出渗漏点。     

红外热像仪在建筑物外墙角结露问题上的应用研究

介绍了建筑物外墙角作为热桥的特点及其对室内环境的不利影响,并指出传统测试方法存在的不足。由于红外热像仪测温方法的特殊性,借助红外热像仪分析外墙角温度场分布。在拟合优度检验确定结露区域温度数据符合Weibull分布的前提下,通过典型热像图探索结露程度与Weibull分布函数参数间的关系,并解释Weibull分布函数参数的具体含义,进一步提出用红外热像仪定量确定结露程度的新方法。     

浅析建筑材料检测在建筑工程中的作用

对于建筑工程而言,建筑材料是其重要构成要素之一,同时也是影响其质量的关键要素。当前,我国建筑材料领域的发展还不够规范,致使一些不合乎标准的建筑材料被应用到建筑工程中,从而影响了建筑工程的质量和寿命。要想使建筑工程的性能有所保障,关键在于抓好建筑材料的检测工作。论文首先论述了建筑材料质量检测的重要性,然后指出检测过程中需要注意的关键环节,最后从试件取样、工作制度、检测设备的应用、检测者的专业素养等四个层面提出了几点合理化建议,旨在为完善我国建筑材料的检测工作提供一定的参考。     

Strategies for In Situ Home Improvement in Romanian Large Housing Estates

Socio-economic and physical change have visibly affected post-socialist cities, yet the state of decay of their inherited large housing estates has only deepened throughout the 1990s, despite the change in tenure through policies of large-scale privatisation. Housing disrepair has now reached a critical stage that requires rapid private and public intervention. This paper examines the extent to which Romanian block residents have been able to improve in situ their housing conditions since 2000, the strategies they employed and the challenges they faced. It focuses on the often ignored private domain of housing, flats and blocks, where changes are also likely to be less visible. By analysing the process of individual utility metering and the practice of collective block management, I argue that besides economics, the unregulated housing context and a relaxed legal culture have challenged individual and collective action and have generated a framework of housing privatism.