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运用有限元软件ABAQUS计算L形带肋钢管混凝土柱阴角相邻两面受火全过程下的耐火极限,分析了阴角邻面受火方式下构件内部温度场和应力场的变化规律,在此基础上分析荷载比、宽厚比、计算长度、加劲肋纵向间距、荷载偏心率、荷载角等参数对耐火极限的影响规律。数据表明:荷载比、计算长度对构件耐火极限影响较大,随着荷载比和计算长度的增大,耐火极限基本呈线性下降;加劲肋间距对构件耐火性能影响较小;由于L形柱的特殊形式,偏心荷载对耐火极限的影响规律较复杂,荷载作用点偏向低温区可以提高耐火极限。 相似文献
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为研究锂离子电池灭火方案,基于火探管灭火技术同时利用新型清洁灭火剂Novec 1230,组装成火探管灭火系统。在灭火测试平台上以功率为200 W的电热管作为外热源引发单电池或电池模组热失控,通过改变火探管的布置位置,记录相应的灭火行为以及灭火效率,并对实验结果进行了分析。研究结果表明,当火探管灭火系统直接布置在电池正上方时,在起火后的5.6s内控制火情;随着灭火剂用量增加可以显著降低体系温度,防止电池复燃以及连锁热失控现象发生;火探管有效覆盖区域外的失控电池作为热源将继续加热临近电池,引发连锁热失控,造成灭火系统失效;根据电池热失控后的燃烧行为以及传热行为,提出相应的火探管灭火系统复合方案。 相似文献
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Fire as a Soil-Forming Factor 总被引:2,自引:0,他引:2
Giacomo Certini 《Ambio》2014,43(2):191-195
In the span of a human generation, fire can, in theory, impact all the land covered by vegetation. Its occurrence has many important direct and indirect effects on soil, some of which are long-lasting or even permanent. As a consequence, fire must be considered a soil-forming factor, on par with the others traditionally recognized, namely: parent material, topography, time, climate, living beings not endowed with the power of reason, and humans. 相似文献
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The chemical composition of the odors typical of fires has recently been deciphered. Basically the constituents are mixtures of acetophenone, benzyl alcohol, hydroxylated derivatives of benzaldehyde, methoxylated and/or alkylated phenols and naphthalene. This finding makes it possible to develop objective, practical analytic measurement methods for the burnt smell as a contribution to improving fire damage assessment and remediation monitoring. With the aid of an artificially produced burnt smell and a panel of testers the odor detection threshold of a test mixture was determined olfactometrically to 2 μg m−3. Using a defined burnt-smell atmosphere in a test chamber, analytical methods with active sampling, the adsorbents XAD 7 and TENAX TA, and GC/MS measurement were then optimized and tested with a view to being able to carry out sensitive quantitative measurement of burnt smells. A further practical method with particular application to the qualitative characterization of this odor is based on the use of a new SPME (solid-phase microextraction) field sampler with DVB/CAR/PDMS (divinylbenzene/Carboxen™/polydimethylsiloxane) fibers. 相似文献
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Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) are unintentional byproducts of combustion and industrial processes. Firefighters face the risk of occupational exposure to PCDD/Fs. Congener-specific analyses of 17 PCDD/Fs were performed on 20 serum samples collected from firefighters and fire scene investigators, and four soot samples that had deposited on the surfaces of the fire helmets and were collected after the firefighters had fought fires. The PCDD/F concentrations on the helmets that were contaminated by being worn at the fire scenes were 63-285 times higher than those on a clean helmet. The median serum PCDD/F concentration of the 16 firefighters (12 pg WHO2005-TEQ g−1 lipid) was not different from those of the males from the general Taiwanese population (9.4 pg WHO2005-TEQ g−1 lipid). However, the median PCDD/F level in the four fire scene investigators (15 pg WHO2005-TEQ g−1 lipid) was higher than those in the male from the general Taiwanese population (Mann-Whitney U test, p < 0.01). Furthermore, the serum samples from the firefighters and fire scene investigators, and the soot samples from the fire scenes presented similarly distinctive PCDD/F profiles that had elevated proportions for 10 PCDF congeners. Limited data indicated that the fire scene investigators were occupationally exposed to PCDD/Fs at the fire scenes. We suggested that the firefighters were not occupationally exposed to PCDD/Fs at the fire scenes due to appropriate protection. However, the fire scene investigators may have had more occupational exposure to PCDD/Fs due to poor protection, and further research must be performed to confirm this. 相似文献
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Ochoa-Hueso R Allen EB Branquinho C Cruz C Dias T Fenn ME Manrique E Pérez-Corona ME Sheppard LJ Stock WD 《Environmental pollution (Barking, Essex : 1987)》2011,159(10):2265-2279
We review the ecological consequences of N deposition on the five Mediterranean regions of the world. Seasonality of precipitation and fires regulate the N cycle in these water-limited ecosystems, where dry N deposition dominates. Nitrogen accumulation in soils and on plant surfaces results in peaks of availability with the first winter rains. Decoupling between N flushes and plant demand promotes losses via leaching and gas emissions. Differences in P availability may control the response to N inputs and susceptibility to exotic plant invasion. Invasive grasses accumulate as fuel during the dry season, altering fire regimes. California and the Mediterranean Basin are the most threatened by N deposition; however, there is limited evidence for N deposition impacts outside of California. Consequently, more research is needed to determine critical loads for each region and vegetation type based on the most sensitive elements, such as changes in lichen species composition and N cycling. 相似文献
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根据一真实火灾调查报告设定了真实大空间建筑物开口情况和材料燃烧性能参数,建立了FDS(Fire Dy-namics Simulator)物理模型。计算了火灾释热速率以及着火大空间烟气的温度场和一氧化碳浓度场的变化。研究结果表明:火灾短时间发生轰燃,随后发生回燃。轰燃是导致大量人员死亡的1个重要原因;回燃没有引起各点烟气的温度和一氧化碳浓度显著的提高,但对各点烟气的温度和一氧化碳浓度的保持起到较大作用。 相似文献