共查询到19条相似文献,搜索用时 218 毫秒
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在已有木结构火灾性能研究资料基础上,分析和总结了木结构火灾特征、木材炭化机理和微观结构变化、木材炭化速度模型、受火木构件剩余承载力、持荷木构件耐火极限等研究现状,并提出了需要进一步研究的重点。 相似文献
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为了研究新型木-钢结构望板系统相对于传统木结构望板系统及冷摊瓦屋顶系统耐火极限性能,该文采用Abaqus模拟软件建立了有限元分析模型。在标准升温曲线下,对三种屋顶系统进行温度场模拟分析。结果得出,随着时间及温度的增加,传统木结构望板系统及冷摊瓦屋顶系统中,木板先于木梁炭化完全;新型木-钢结构望板系统中,木板后于木梁炭化完全且上下两板炭化速度有明显改变。之后对三种屋顶系统在同等荷载作用下,进行结构场分析,结果表明:新型木-钢结构望板系统耐火极限相对于传统木结构望板系统提高73%,相对于冷摊瓦系统提高52%。得出新型木-钢结构望板系统具有更好的耐火性能,可为村镇木结构建筑和改造提供参考。 相似文献
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采用剩余截面法计算分析了典型截面胶合木构件的耐火性能,并对平面尺寸7.2 m×7.0 m、高度4.5 m 的胶合木结构进行了实体火灾试验。结果表明,胶合木构件耐火性能受荷载比和升温曲线影响较大,在90%荷载比时,截面尺寸200 mm×400mm 的胶合木梁耐火极限约为50 min。ISO 834 标准升温曲线与大空间升温曲线下作用75 min,截面尺寸220 mm×280 mm 的构件截面炭化深度分别约40 mm 和30 mm。无外部火源时,胶合木结构难于延燃,火蔓延范围有限。从胶合木截面炭化深度计算、构件耐火极限计算到胶合木结构实体火灾试验得到的结果,可为工程中胶合木结构抗火性能分析提供参考。 相似文献
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为研究木结构建筑中正交胶合木(CLT)楼板耐火性能,通过两组四块CLT楼板池火对比试验,探究不同油盘直径池火火源及CLT楼板试件不同截面厚度对CLT楼板耐火性能的影响。结果表明,CLT楼板在池火持续加热燃烧过程中,木材热解产生可燃气体被池火火焰点燃,使试件受火面火焰两次增大并蔓延至构件边缘;随着油盘直径增大,CLT楼板耐火时间明显缩短,耐火性能显著降低;截面厚度为20mm的CLT楼板池火试验过程中均被烧穿,平均炭化速度最高达1.538mm/min。截面厚度为25mm的CLT楼板受火45min时均未烧穿,有效阻挡火焰向背面蔓延。适当增加构件厚度,其构件耐火性能明显提高。 相似文献
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笔者在参与我国现行《高层民用建筑设计防火规范》GB50045—95(以下简称《高规》)的管理工作过程中,有设计单位的设计人员来函询问如何确定采用后张法施工的预应力构件的耐火极限问题。《高规》附录A——“各类建筑构件的燃烧性能和耐火极限”中的80%以上的数据是公安部四川消防科学研究所于70年代,通过作构件的耐火试验得出的,该附录对各类预 相似文献
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传统木结构建筑木构件表面通常采用地仗处理进行保护,而地仗处理对木构件耐火性能的影响规律尚不清晰。为此,通过4组10根三面受火木梁耐火极限的对比试验,研究了截面尺寸、持荷水平、是否地仗处理等因素对木梁耐火极限的影响规律,提出了剩余截面法计算木梁耐火极限,并提出了木梁热力耦合数值分析模型。结果表明,三面受火木梁耐火极限随持荷水平的增加明显降低,当持荷比由30%增加至50%时,木梁耐火极限降低19.6%~31.7%,平均降低17.5min;三面受火木梁耐火极限随截面尺寸增加显著提高,当截面尺寸由100mm×200mm增加至200mm×400mm时,耐火极限提高95.1%~107.8%,平均增加40.0min;木梁表面经一麻五灰地仗处理后,耐火极限提高21.3%~429%,平均提高15.8min。不同持荷水平和截面尺寸木梁内部距离边缘相同位置处的温度变化相近,表面采用一麻五灰地仗处理可显著延缓木梁内部温度的上升速率,木梁两个方向的炭化速度平均值为0.54mm/min,与未作表面处理的木梁相比降低19.4%。基于剩余截面法和数值模拟得到的三面受火木梁耐火极限预测值与试验值的误差在±15%以内,基本满足工程精度要求。 相似文献
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The fire design of timber structures usually take into account both the loss in cross-section due to charring of wood and the temperature-dependent reduction of strength and stiffness of the uncharred residual cross-section. The fire behaviour of timber assemblies made of hollow core elements is characterised by different charring phases. After the fire exposed timber layer is completely charred and the char-layer has fallen off, the thin vertical timber members are exposed to fire on 3 sides, leading to very irregular residual cross-sections with charring depths much greater than for heavy timber structures. Based on an extensive experimental and parametric study, a simplified calculation model for the fire resistance of timber slabs made of hollow core elements has been developed. The calculation model bases on the reduced cross-section method and takes into account two different charring phases. The paper first describes and discusses the simplified calculation model, and then compares the test results to the calculation model. 相似文献
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随着生活水平的提高,商业建筑越来越在人们的日常生活中占据了重要地位。与此同时,商业建筑的火灾也带来了经济和生命安全上的危险。我国现行的防火规范主要为《建筑设计防火规范》(GB50016-2014),是针对普遍性的建筑,商业建筑因人们对其特殊的需求,具有其特殊性,通常具有体量大、结构复杂、可燃物多、功能复杂等特点。本文从研究目的、商业建筑的火灾特点和疏散影响因素、现行的综合性商业建筑安全疏散设计等方面对综合性商业建筑防火疏散做出研究,为提出性能化防火设计新思路作好铺垫工作。 相似文献
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对GB 51249-2017《建筑钢结构防火技术规范》中的关键条文进行解读,并基于规范与数值模拟实验进行钢结构抗火计算的对比研究.结果表明:规范对静定结构中的三面、四面受火的钢构件适用性好;对于超静定结构中的三面、四面受火钢构件,适用性有待进一步研究. 相似文献
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通过3攒清式木结构斗拱耐火性能的足尺明火试验,研究不同防火处理方式对斗拱耐火性能的影响规律。选取单翘单昂五踩平身科斗拱为研究对象,火源采用木垛火。结果表明:明火试验中,斗拱试件单才瓜拱、单才万拱、厢拱等组件首先被引燃且燃烧持续时间最长,炭化较严重。未进行表面处理的斗拱组件燃烧火焰与木垛火源叠加,火苗高度较高;组件阻燃涂料浸渍的斗拱试件受火过程中组件木材未被引燃。随着受火时间增加,不同位置的温度大部分有不同程度的升高,不同试件距边缘相同位置处的温度变化规律大致相近。各组件沿其轴线方向的炭化不均匀,且各组件炭化速度与空间位置和原始尺寸有关。翘、单才瓜拱、厢拱、单才万拱和外拽枋等组件的宽度和高度方向的炭化速度均较高。表面未处理试件各组件炭化速度为0.5~1.0mm/min,表面喷涂阻燃涂料试件各组件炭化速度为0.1~0.9mm/min,组件采用阻燃涂料浸渍处理试件各组件炭化速度为0.1~0.7mm/min。 相似文献
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通过国家建筑标准设计14X505-1《〈火灾自动报警系统设计规范〉图示》中关于住宅建筑火灾自动报警系统的内容,介绍如何应用GB 50116-2013《火灾自动报警系统设计规范》设计住宅建筑、住宅建筑群及住宅小区的火灾自动报警系统,重点解析住宅建筑火灾自动报警系统分类、总线短路隔离器、家用火灾报警控制器、火灾警报器、消防应急广播、可燃气体探测器等的设置要求。 相似文献
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D.J. Hopkin J. El-Rimawi V. Silberschmidt T. Lennon 《Construction and Building Materials》2011,25(5):2584-2595
Timber, like other structural materials such as concrete and steel, has its own Eurocode (Eurocode 5 part 1.2) for the structural fire design of buildings. However unlike other fire parts of the Eurocodes it is not widely adopted due to its inherent limitations. With the exception of a single Annex, the timber Eurocode (EN 1995-1-2) is only applicable to standard fire exposure. Annex A gives guidance on the charring rates of initially un-protected timber members in parametric fires, however in the UK the use of the Annex is prohibited by the national Annex to the code.The concrete and steel industries have undoubtedly benefited from performance based design whereby the structural fire design strategy is centred on a design fire (typically a parametric fire), which is more credible than the standard fire curve. Such an approach has resulted in more flexible, innovative buildings which have been designed based upon fundamental structural mechanics at elevated temperature, using advanced numerical models. At present however the same principals cannot be applied to the advanced fire design of timber buildings due to current limitations in the timber Eurocode. Where advanced calculation procedures are considered by the code (Annex B), much like many of the methods contained therein, the procedures are only applicable to standard fire exposure.The scope of applicability of the code stems from a fundamental problem regarding a lack of understanding of the heat transfer characteristics of timber in natural fires. The thermo-physical properties contained in the code are ‘effective’ properties. This essentially means that they are calibrated against test results to account for a lack of understanding regarding mass transfer, cracking and ablation both within the timber and char layer. Such calibrations have only been performed on timber members exposed to standard furnace conditions.To attempt to overcome this barrier and extend the scope of thermo-physical properties in the code a study has been undertaken to establish how the conductivity properties of the char layer influence the depth of char in parametric fires. Through calibration of an effective conductivity of the char layer against the parametric charring method contained in Annex A of EN 1995-1-2, it has been possible to establish a relationship between ‘heating rate’ and the effective conductivity of the char layer, in the heating phase of parametric fires. The modified conductivity model is shown to be applicable to a range of densities and moisture contents of timber and also variations in heating rate and fire load density. The latter is a direct result of the method used in the adaptation of the properties. The modified model is objectively critiqued and proposed further work is discussed in detail. The applicability of the modified model in the cooling phase of fires is also discussed. 相似文献