【作者】 王珍；

【导师】 黄涛；

【作者基本信息】 西南交通大学 ， 市政工程， 2011， 博士

【摘要】 建筑物一旦发生火灾,必须及时进行灭火,以扑灭火焰和阻止火焰的传播蔓延,防止火势的扩大,将火灾损失降到最低。消防射水是最常用的灭火方式,通过对着火物进行射水,可以对正在燃烧的材料进行降温、覆盖燃烧物窒息火焰、水蒸气稀释氧气、抑制燃烧链反应的方式阻止燃烧；同时对可燃材料射水,降低可燃材料的温度和增加可燃材料的湿度,阻止火势的蔓延传播。消防射水在扑灭建筑火灾的时候,消防射水对经受高温后性能严重劣化的混凝土必然会产生一定的影响,水-火耦合作用可能会加速混凝土性能的劣化,使建筑结构损毁和承载力急剧下降,导致建筑结构的局部或整体性坍塌。作为建筑的承重和支撑体系,即使是在火灾和消防射水的共同作用下,也必须在一定时间内保持足够的承载能力,保证受灾人员能安全的撤离火灾现场、消防战斗人员能安全的进行灭火战斗和救护人员能安全的救护伤员。本文深入研究了高性能混凝土的耐火性能衰减规律,探究了消防射水与火灾共同作用下的高性能混凝土建筑的坍塌机理,建立了高性能混凝土建筑火灾后的坍塌预测和评价方法,为确定火灾后其残余承载力,从而延长结构受火时坍塌的时间提供了科学依据,为高性能混凝土结构火灾损伤后期诊断评估与修复加固提供了基础参数。本文主要研究内容和成果如下：1、高性能混凝土火灾烧损试验研究(1)对高温后C35、C40、C50高性能混凝土与掺防腐剂C35高性能混凝土的残余抗压强度进行了对比试验,分析了高性能混凝土爆裂原因,总结了试件外观特征随火场温度的变化规律,建立了火灾后HPC残余抗压强度与火场温度之间的关系式。研究表明：消防射水对建筑火灾后C35HPC的残余抗压强度有很大影响,自然冷却条件下,HPC的残余抗压强度整体呈衰减状态,300℃时略有升高；在射水冷却条件下,HPC的残余抗压强度始终呈衰减状态；在相同温度条件下,采用自然冷却方式测得的HPC的残余抗压强度均高于采用射水冷却方式测得的HPC的残余抗压强度,自然冷却条件下HPC的残余抗压强度最高的约为射水冷却条件下HPC的残余强度的13倍。(2)研究了高温过程中HPC的残余抗压强度的变化规律；对比分析HPC在高温过程中与高温自然冷却后残余抗压强度的异同。研究表明：300℃～400℃时,HPC残余强度在明显有所波动,但是冷却后的HPC残余抗压强度没有高温中残余抗压强度上升的那么明显；相同加热温度条件下,高温过程中HPC的残余抗压强度高温略高于自然冷却后HPC的残余抗压强度。2、公路隧道衬砌高性能混凝土的高温烧损试验研究以隧道常用的C50 HPC为研究对象,开展了HPC试件高温烧损试验,研究了高温后受损衬砌混凝土残余抗压强度在不同条件下随经历温度劣化的规律和定量关系,建立了火灾后隧道衬砌HPC残余抗压强度与火场温度之间的数学关系式。研究表明：高等级的HPC抗压强度很高,但其抗火性能却很差；在高温但过程中及自然冷却条件下,HPC残余抗压强度总体上呈降低趋势,在300℃时,C50HPC残余抗压强度有小幅增加；射水冷却条件下,HPC残余抗压强度随着温度升高一直呈衰减状态；相同加热温度等级条件下,高温过程中HPC的残余抗压强度略高于自然冷却后HPC的残余抗压强度,自然冷却后HPC的残余抗压强度高于射水冷却后HPC的残余抗压强度。3、抗蚀防腐剂对高性能混凝土耐火性能的影响对高温后掺抗蚀防腐剂高性能混凝土的残余抗压强度试验,描述了高温过程试验现象,分析了掺抗蚀防腐剂高性能混凝土爆裂原因,探索添加防腐剂对高温后高性能混凝土残余抗压强度的影响；通过回归分析建立了掺抗蚀防腐剂高性能混凝土抗压强度与温度之间的二元线性回归公式。研究表明：掺加抗蚀防腐剂高性能混凝土试件在400℃时就发生爆裂,而未掺抗蚀防腐剂高性能混凝土试件在试验过程中没发生爆裂现象,表明虽然掺抗蚀防腐剂有利于增强高性能混凝土抗压强度,但是不利于高性能混凝土抗爆裂性能。4、消防射水对持续燃烧建筑物坍塌的影响分析对特定功能建筑物火灾荷载进行了统计分析,并根据火灾动力学原理和概率统计原理,给出了特定功能建筑因持续燃烧致建筑坍塌的概率函数和有消防射水灭火情况下建筑物在火-水耦合损伤下坍塌的概率函数。根据分析,混凝土建筑构件在火-水耦合损伤下会降低其实际耐火时间,消防射水直接冷却高温混凝土会增加混凝土构件坍塌的概率。当建筑物构件耐火时间较小时,消防射水对建筑构件坍塌的影响较小,其坍塌概率主要受建筑构件在持续受火条件下吸收的热荷载决定；当建筑构件的耐火时间较大时,必须考虑消防射水对持续燃烧建筑构件坍塌的影响。更多还原

【Abstract】 Prompt fire suppression is needed once a building fire disaster occurs in order to extinguish the flames, stop flame spread and minimize the damage. Fire-fighting water jetting (FFWJ) is a common method for fire extinguishment, which could stop combustion through water jetting to fire, cooling and covering the comburent, diluting the oxygen by water vapor and suppressing the combustion chain reaction. Moreover, FFWJ could also prevent fire spread though decreasing the temperature and increasing the moisture of comburent. However, the FFWJ would affect the performance of the concrete, which deteriorates in the high temperature environment. The effects of water-fire-coupling may accelerate the deterioration of concrete performance, damage the structure and decrease the bearing capacity of the buildings and finally lead to partial or whole collapse. As the bearing structural system, the high-performance concrete (HPC) must have sufficient bearing capacity in a certain period of time after the fire disaster occurs in order to assure evacuation, fire-fighting and rescue.The present research studied the deterioration of the HPC, explored the mechanism of the collapse of the HPC concrete building, and proposed the collapse prediction and evaluation method in order to provide scientific basis for determining the building bearing capacity and the endurance time after fire disasters, and to provide data for the damage analysis and evaluation of the HPC and building restoration.The research contents and results of this study were as follows:1、Damage analysis of the HPC after fire disasters(1) In order to analyze the reasons for the HPC burst, the pressive strengths of HPC C35, C40 and C50 were compared with C35-A (C35 mixed with anticorrosive). The variation of external characteristics of concretes associated with fire temperature was summarized, and the relationship between the HPC bearing capacity and fire temperature was analyzed. The results indicated that the bearing capacity of HPC C35 was strongly affected by FFWJ. In the common cooling condition, the HPC bearing capacity decreased with temperature in general except for a slightly increase at 300℃; In the FFWJ condition, however, the HPC bearing capacity decreased all along with temperature. Moreover, the HPC bearing capacity in the common cooling condition was higher than that in the FFWJ condition at the same temperature. The maximum HPC bearing capacity in the common cooling condition was 1.3-fold of that in the FFWJ condition.(2) The variation of the HPC bearing capacity under high temperature was analyzed and the HPC bearing capacity under high temperature and after common cooling was compared. The results showed that the HPC bearing capacity fluctuated significantly with the temperature ranging from 300℃to 400℃, whereas the fluctuation was less marked at lower temperature. The HPC bearing capacity in high temperature process was slightly higher than that after common cooling at the same temperature.2、Damage experiment of the highway tunnel lining HPCThis experiment was conducted with HPC C50, which was widely used in highway tunnels, to explore the relationship between the bearing capacity and the fire temperature in different conditions. The results revealed that high-grade HPC showed low fire-resistant capacity despite of the high strength; in the common cooling condition, the bearing capacity of HPC C50 decreased generally with temperature except for a slightly increase at 300℃; In the FFWJ condition, however, the HPC bearing capacity decreased all along with temperature. Furthermore, the HPC bearing capacity in high temperature process was slightly higher than that after common cooling at the same temperature, while the HPC bearing capacity in the condition of common cooling was higher than that in the condition of FFWJ at the same temperature.3、The effects of the anticorrosive on the HPC fire-resistant capacityIn this experiment, the bearing capacity of HPC mixed with the anticorrosive was determined after the high temperature process, the phenomenon during the process was described, the reasons for the burst of the HPC mixed with the anticorrosive was analyzed, and the effects of the anticorrosive on the HPC bearing capacity was explored as well; Regression analysis revealed that the relationship between the bearing capacity of HPC mixed with the anticorrosive and temperature could be described by linear equation in two unknowns. Moreover, the result showed that the HPC mixed with the anticorrosive burst at 400℃, whereas the HPC without the anticorrosive did not burst during the experiment, indicating that the anticorrosive may help to increase the HPC bearing capacity, but may be adverse to the increase of HPC anti-burst capacity.4、The effects of FFWJ on the collapse of blazing buildingsBased on the fire dynamics theory and probability statistics, the building fire loads were analyzed, and the collapse probability function of given buildings due to sustained combustion and the collapse probability function of given buildings due to water-fire-coupling in the condition of FFWJ were proposed. The results indicated that the fire endurance time of the HPC decreased with the water-fire-coupling damage, and cooling by FFWJ increased the HPC collapse probability. when the HPC fire endurance time was short, FFWJ showed little effects on the building collapse; when long, the collapse probability was mainly determined by the themal load of the building during sustained combustion. It was proposed that the effects of FFWJ on the collapse of buildings should be considered when the fire endurance time was long.更多还原