【作者】 侯炜；

【导师】 贺拴海；

【作者基本信息】 长安大学 ， 桥梁与隧道工程， 2014， 博士

【摘要】 近年来，随着交通量的迅猛增加以及运输工具的多样性，桥梁火灾事故频频发生，运输易燃易爆物品的车辆日渐增多，交通事故和人为原因引起的桥梁火灾成为交通基础设施新的威胁。火灾作为桥梁的偶然荷载，对结构造成不可估量的破坏，轻者势必影响交通质量，造成人身伤亡和经济损失，重者可造成桥梁永久破坏与坍塌。目前关于桥梁火灾的研究主要集中在火灾下预应力混凝土（以下简称“PSC”）结构及钢筋混凝土（以下简称“RC”）结构整体及局部抗火性能，涉及火灾后RC整体及局部抗火性能较少，对于火灾后PSC结构的抗火性能研究更少。本文以国家自然科学基金“火灾下混凝土桥梁有效预应力衰变机理与承载能力分析方法研究（51308056）”；交通运输部交通建设科技项目“火灾下桥梁结构灾变机理及安全性评价与加固技术研究（2011318812970）”为依托，针对预应力混凝土箱型梁桥整体抗火性能，以模型试验结合数值模拟进行了系统研究。主要研究工作有：基于各规范、学者的调研，对高温作用后预应力混凝土材料的强度、弹性模量及本构关系进行计算模型的整理与分析，并对使用率高的计算模型进行分阶段选取、分布拟合的方法获得高温作用后预应力混凝土材料各力学性能指标（强度、弹性模量及本构关系）的拟合计算模型。对3片试验梁（对比梁PSB-1、无防火涂层试验梁PSB-2、有防火涂层试验梁PSB-3）进行火灾下及火灾后的模型试验研究。基于火灾下试验梁的温度场、位移时程及预应力损失等数据分析，揭示了防护涂层对PSC结构抗火性能的影响程度。基于火灾后试验梁的位移、应变及刚度、频率等数据分析，给出了PSC结构火灾后的剩余承载能力及动力特性状况。通过测定混凝土试块高温后的抗压强度，并对比未受高温的试块，研究了膨胀型防火涂料不同厚度对混凝土结构的防火保护作用，给出了强度折减的经验公式。通过对受火梁按由底至顶及烧损深度的方法来测定混凝土强度，计算混凝土强度值，揭示了受火后混凝土强度沿梁高及烧损深度的变化规律。研究分析了EUROCODE、ASTM-E119、JISA1304及ISO834等多种火灾升温计算模型，明确了火灾分析采用的升温模型和理论计算方法，通过对比火灾过程中结构温度场的试验数据，揭示了结构温度场由外至内的热传导规律，并运用大型通用软件建立有限元模型，进行温度场的非线性分析，通过与实测值对比，验证了模型的正确性。运用大型通用有限元分析软件对3片试验梁进行模拟，通过设定材料不同的本构关系，并依照试验的边界条件建立有限元模型，模拟试验梁在荷载作用下的挠曲变形、混凝土应变以及试验梁的极限承载力、固有频率等，通过与实测值的对比，验证了模型的有效性。更多还原

【Abstract】 In recent years, with the rapid increase in traffic as well as diversity, bridges’ fire occursfrequently with increasing number of vehicles in transporting flammable substances. Trafficaccidents and man-made causes fire accidents on bridge become a new threat to thetransportation infrastructure. Accidental fire as a bridge load causes incalculable damage tothe structure, the light is bound to affect the quality of traffic, causing personal injury andeconomic loss, the severe can cause permanent damage to the bridge and its collapse. Currentresearch of bridge fire mainly focuses on overall and local structural fire resistance ofstructural under fire of the prestressed concrete (hereinafter referred to as "PSC") structureand reinforced concrete (hereinafter referred to as "RC"), research less involves overall andlocal structural fire resistance of structural after fire and the PSC structure in fire resistanceresearch is less than the former.This paper takes the National Natural Science Foundation"Research analysis ofprestressed concrete bridge decay mechanism and effective carrying capacity under fire(51308056)"; Ministry of Transport and Communications Construction Technology Project"under the bridge structure fire disaster mechanism and safety evaluation and reinforcementtechnology research (2011318812970) as the basis for the overall fire resistance ofprestressed concrete box girder bridge, studied on the model test and numerical simulation.The main research work are:Based on survey data on criterion and abroad, to collate prestressed concrete materials,elastic modulus and constitutive relation after the high temperature strength and analyzecomputational models, and the use of high computational model selected by the line instages, distribution fitting each mechanical properties of concrete materials (strength, elasticmodulus and constitutive relation) model fitting method to obtain high temperature afterprestressing.Three beam (contrast beam PSB-1, no fire protection coating beam PSB-2, fireproofcoating beam PSB-3) are tested research model under fire and after fire. Based on the testbeam temperature field under fire, when the displacement process and prestressing losses ofdata analysis, the protective coating to reveal the extent of the impact on the fire resistance ofstructural PSC. Test beam displacement, strain and stiffness, frequency-based data analysisafter the fire, given the remaining carrying capacity and dynamic characteristics of thesituation after the PSC structure fire. By measuring the compressive strength of concrete block after high temperature,comparing concrete blocks without high temperature and study on different thicknessintumescent fire protective coatings of concrete structures and give the empirical formula ofstrength reduction. Through the fire from the bottom to the top of the beam and by burningmethod to determine the depth of the concrete strength, concrete strength values calculated toreveal the changes in the law after the concrete strength by the fire burning along the beamheight and depth of the subject.Study and analyse the EUROCODE, ASTM-E119, JIS A1304and ISO834computational fire model, a clear warming on models and theoretical calculation methodsused in the analysis of fire, fire process by comparing the temperature field trial datastructures, revealing the structure of temperature field from the outside to the inside of theheat conduction law, and the use of large general-purpose finite element software model fornonlinear analysis of temperature field, by comparison with the measured values to verify thecorrectness of the model.The use of large-scale finite element analysis software for three test beams to simulatethe material by setting different constitutive relations and finite element model of the test inaccordance with the boundary conditions, the simulation test beam deflection under load,the concrete strain and ultimate bearing capacity of the test beams, natural frequency, etc.,by comparing the measured values, and the validity of the model.更多还原