预应力混凝土箱梁结构抗火性能研究

发布时间：2018-04-30 14:11

本文选题：预应力混凝土箱梁 + 火灾　；参考：《长安大学》2014年博士论文

【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。
[Abstract]:In recent years, with the rapid increase of traffic volume and the diversity of means of transport, bridge fire accidents occur frequently, and the number of vehicles transporting flammable and explosive items is increasing. Traffic accidents and man-made bridge fires have become a new threat to traffic infrastructure. Fire, as the accidental load of bridge, causes inestimable damage to the structure. The lighter is bound to affect the traffic quality, resulting in casualties and economic losses, and the heavy can cause permanent damage and collapse of the bridge. At present, the research on bridge fire mainly focuses on the whole and local fire resistance of prestressed concrete (PSC) structure and reinforced concrete (RC) structure under fire. The overall and local fire resistance of RC structures after fire is less than that of PSC structures after fire. In this paper, the National Natural Science Foundation of China "effective Prestress decay Mechanism and bearing capacity Analysis method of concrete Bridges under Fire" (51308056); Based on the science and technology project of traffic construction of Ministry of Communications and Transport, "study on disaster Mechanism and Safety Evaluation and reinforcement Technology of Bridge structure under Fire", aiming at the overall fire resistance of prestressed concrete box girder bridge, The model test and numerical simulation are used in this paper. The main research work is: Based on various codes and scholars' research, the strength, elastic modulus and constitutive relation of prestressed concrete materials after high temperature action are analyzed and analyzed, and the calculation models with high utilization rate are selected in different stages. The fitting model of mechanical properties (strength, elastic modulus and constitutive relation) of prestressed concrete after high temperature action was obtained by the method of distribution fitting. The model tests of three test beams (PSB-1, PSB-2 and PSB-3) were carried out under fire and after fire. Based on the analysis of the temperature field, displacement time history and prestress loss of the test beam under fire, the influence of the protective coating on the fire resistance of PSC structure is revealed. Based on the analysis of the displacement, strain, stiffness and frequency of the test beam after fire, the residual bearing capacity and dynamic characteristics of the PSC structure after fire are given. By measuring the compressive strength of concrete specimens after high temperature and comparing the unheated specimens, the fire protection effects of different thickness of expansive fire resistant coatings on concrete structures are studied, and the empirical formula of strength reduction is given. The concrete strength was measured by the method of bottom to top and burning depth of fire beam, and the concrete strength value was calculated. The variation rule of concrete strength along the beam height and burning depth after fire was revealed. Several fire heating calculation models, such as EUROCODEN ASTM-E119JISA1304 and ISO834, are studied and analyzed. The heating model and theoretical calculation method used in fire analysis are defined. The experimental data of structure temperature field during fire are compared. The heat conduction law of the structure temperature field from outside to inside is revealed, and the finite element model is established by using a large scale general software, and the nonlinear analysis of the temperature field is carried out. The correctness of the model is verified by comparing with the measured data. Three test beams are simulated by using a large and universal finite element analysis software. By setting up different constitutive relations of materials and establishing a finite element model according to the boundary conditions of the test, the flexural deformation of the test beams under load is simulated. The concrete strain and the ultimate bearing capacity and natural frequency of the test beam are compared with the measured values to verify the validity of the model.
【学位授予单位】：长安大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：U447;U441

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