【作者】 王翠娟；

【导师】 贺拴海；

【作者基本信息】 长安大学 ， 桥梁与隧道工程， 2013， 博士

【摘要】 对于交通基础设施，火灾是最严重的灾害之一。近年来，随着交通量的迅猛增加以及运输工具的多样性，桥梁火灾事故频现，穿越公路的重型硬脂酸车、苯酚运输车、运油(气)卡车、海上油(气)轮日渐增多，交通事故和人为原因引发的火灾对公路桥梁带来了新的威胁。作为桥梁偶然荷载之一的火灾对大桥造成的破坏不可估量，桥梁火灾不仅影响交通质量，造成巨大经济损失，而且重者可造成桥梁的永久损失、甚至坍塌。目前关于桥梁火灾的研究仅停留在单梁及局部结构体系阶段，还未涉及桥梁结构的整体抗火性能，与实桥工程应用的目标还有较大距离。本文以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）”之专题3—“火荷载作用下具有砼桥面的大型梁桥结构影响参数研究”为依托，基于长安大学中央高校基金项目（CHD2011TD010），针对多梁式混凝土T型梁桥结构整体抗火性能，建立了火灾温升模式，设定了火灾场景，综合各材料高温特性和温升曲线，提出了火灾全过程混凝土烧深时程关系公式和累积烧损时程关系公式，研究了桥面不同区域火灾模式下和桥下不同梁肋火灾模式下多梁式混凝土T型梁桥空间变形及应力分布性态，揭示了火灾全过程多梁式混凝土T型梁桥结构的力学性能变化规律，建立了基于分层算法的T型混凝土梁桥火灾全过程剩余刚度与剩余承载力计算模型，提出了基于抗火涂层厚度及导热性能的实体结构温度计算公式，为火灾后桥梁结构的准确评估奠定了基础，为提出桥梁抗火设计实用计算方法提供了丰富的数据。主要研究工作有：（1）研究了空间单元的温度梯度与温度传导率之间的变化关系，考虑混凝土的结晶水随延火温度的变化状态，研究了结晶水随温度变化的潜热函数和单元瞬态温度场传导矩阵方程。基于温度热传导的虚拟层法，提出了混凝土加筋实体单元截面分层温差应力随延火时间和温度变化的计算方法，推导了单向火灾作用下混凝土加筋截面内力计算随延火时间和温度变化的应力应变矩阵，建立了影响结构内力变化的敏感矩阵模型。（2）研究了热力耦合场结构分析所采用的多维加筋单元的计算假定与条件及力学行为和破坏准则，综合考虑热应变增量、塑性应变增量、子步间迭代的应力总量，采用修正增量迭代法得到单元修正坐标系下的计算总应变。（3）研究并分析比较了ISO834、ASTME119和HC及HCM火灾温升曲线，对多梁式梁桥桥面火灾、桥下火灾场景进行了设定、归类并明确了火灾分析的温升模式和计算方法，建立了桥面整跨火灾模式、桥面局部火灾模式、桥下整跨火灾模式、桥下局部火灾模式及桥面和桥下局部火灾模式，给出了形成完整火灾场景的计算条件。（4）选择不同的火灾模式分析混凝土烧损深度，研究了延火时间、ISO834火灾温升模式、HCM火灾温升模式与混凝土烧损深度的时变规律，拟合提出了基于ISO834火灾温升模式和HCM火灾温升模式的火灾全过程混凝土烧损深度的时程关系公式。继而，分析了不同火灾模式下的混凝土累积烧损深度的延时变化规律，采用等效刚度和强度换算厚度的计算方法，拟合提出了基于ISO834火灾温升模式和HCM火灾温升模式的火灾全过程混凝土累积烧损深度的时程关系公式。（5）基于高温场焓传导模型，利用热-力耦合方法研究了桥面不同区域、桥下不同梁肋火灾全过程混凝土T型梁桥的空间变形与应力分布状态，揭示了火灾全过程多梁式混凝土T型梁桥实体剪力滞空间变化规律和时程剪力滞比的包络规律。①研究了多梁式混凝土T型梁桥多区域跨中桥面受火模式，分析了此模式下多梁式混凝土T型梁桥各梁肋截面关键点温度时程变化规律及温度应力场分布，计算了钢筋应力时程分布及梁肋与关键点挠度在自重荷载作用下的变化规律，揭示了桥面对称火荷载作用下多梁式混凝土T型梁桥实体剪力滞空间变化规律和时程剪力滞比的包络规律。②研究了多梁式混凝土T型梁桥桥下不同梁肋受火模式，分析了此模式下多梁式钢筋混凝土T梁桥各梁肋截面关键点温度时程变化规律及温度应力场分布，计算了梁肋与关键点挠度在自重荷载作用下的变化规律，揭示了桥下对称火灾全过程多梁式混凝土T型梁桥实体剪力滞空间变化规律和时程剪力滞比的包络规律。（6）考虑混凝土烧损深度和延火时间及温度的时域分布，采用截面有效高度的计算方法，提出了桥面、桥下火灾全过程混凝土梁桥剩余刚度时程修正计算公式，并对剩余刚度时程修正计算公式进行了相对偏差估计；提出了桥面、桥下火灾全过程混凝土T型梁桥剩余承载能力时程计算公式。研究了抗火涂层不同导热系数和不同厚度下混凝土T型梁截面的温度时程分布和温差时程分布，拟合提出了抗火涂层不同导热系数和不同厚度下混凝土实体结构的温度计算公式。更多还原

【Abstract】 Fire is one of the most severe hazards to transportation infrastructure subjected duringtheir lifetime. In recent years with the rapid increase of traffic and the diversity oftransportation, fire hazard in bridges is frequent. When increasing transport vehicles filledwith stearinic acid and phenol and oil as well as gas is riding on the highway, a great threat tobridge caused by fire hazard has a tough issue as a result of traffic accidents and human factor.Bridge fires as one of accidental load can lead to significant economic and public losses,what’s more, permanent loss or collapse. The current research presenting an overview of firehazard in bridges is only stayed in the stage of single beam and local structure, which it ishard to be applied actually.Based on study on catastrophe mechanism and strengthening for concrete bridgestructure exposed to fire(Grant No.2011318812970) sponsored by Research Fund Ministry ofTransport of the People’s Republic of China, and Study on thermodynamics model and heatconduction mechanism for concrete bridge exposed to fire(Grant No. CHD2011TD010)sponsored by Research Fund for the Central Universities of China, fire temperature rise modelis established and fire scenarios is designed. Material properties and temperature rise curveare comprehensively putted into consideration, time-dependent formula of burning depth andcumulative burning damage depth for concrete is proposed. The deformation and stressdistribution of multi-beam concrete T-shaped section beam girder are studied under conditionof different fire mode. Fire-resistant performance of structure is revealed. Residual stiffnessand bearing capacity calculation formulae are suggested. Temperature calculation formulaincluding coating thickness and thermal conductivity is constructed on the basis of laminatealgorithm. All of these laid a foundation for fire designation and evaluation. The mainresearch contents are as follows:(1)The relationship between temperature gradient and temperature conductivity of spaceelements is studied. Based on variation of crystalliferous water in concrete, the latent heatfunction of crystalliferous water is studied with increasing temperature, then, thermalconduction matrix equation of elements in transient temperature field is obtained. Based on virtual layer method of heat conduction, calculation method of thermal stress for reinforcedconcrete solid is proposed, and the stress-strain matrix of structure internal force calculationfor reinforced concrete beam exposed to one-way fire is deduced, with extending time andincreasing temperature. also, sensitivity matrix of structure internal force is set up.(2)In the thermo-mechanical coupling analysis, calculation assumptions and mechanicalbehavior and failure criterion of multidimensional reinforced element is studied. Withmodified increment iteration method, total strain of element is gained, which includingthermal and plastic strain increment and total stress of iteration, in modified coordinatesystem.(3)The temperature rise curves such as ISO834and ASTM119and HC and HCM isstudied, fire hazard scene including deck fire and underbridge fire is set and classed in orderto put forward kinds of fire model, for example, deck span fire model, deck local fire model,underbridge span fire model, underbridge local fire model, combining deck and underbridgelocal fire model. all in all, the calculation condition of perfect fire scene is proposed.(4)Based on different fire temperature rise model, the time-dependent relationship amongsome parameters including ISO834model and HCM model and concrete burning depth isstudied, and time-dependent formula of burning depth during process of fire is fitted andproposed. Meanwhile, time-dependent formula of cumulative burning damage depth duringthe whole process of extending fire is put forward by step of the equivalent stiffness andstrength calculation method on the basis of reaearch on variation of cumulative burningdamage depth.(5)Based on high-temperature enthalpy conduction principle, thermo-mechanicalcoupling analysis method is applied to analyzed the variation law of space deformation andstress distribution and solid shear-lags for concrete T-shaped section beam girder undercondition of kinds of deck and underbridge fire model, are studied.①Temperature and stress distribution is studied for deck fire model, and time-dependentcurves of key point for every beam is obtained. During the whole process of extending fire,variation of transverse deflection under dead loads is calculated. At last, the time-dependentvariation of maximum and minimum shear-lags ratio for multi-beam concrete T-shapedsection beam bridges exposed to symmetrical underbridge fire is disclosed. ②Temperature and stress distribution is studied for underbridge fire model, andtime-dependent curves of key point for every beam is obtained. During the whole process ofextending fire, variation of transverse deflection under dead loads is calculated. At last, thetime-dependent variation of maximum and minimum shear-lags ratio for multi-beam concreteT-shaped section beam bridges exposed to symmetrical underbridge fire is disclosed.(6) Based on the burning depth and extending time of fire and temperature distribution ofconcrete, effective height calculation method of section is adopted to put forward thetime-dependent amendment formula of residual stiffness under condition of deck andunderbridge fire model, which the relative deviation estimated is located in acceptedinterval. Then, the residual bearing capacity calculation formula for concrete beam bridge isproposed under condition of each fire model. In addition, thermal conductivity and thicknessof the fire-resistant coat focused on is analyzed to expose time-dependent temperaturedistribution and temperature difference distribution for the concrete T-shaped section beam,and calculation formula of temperature for concrete solid structure is proposed.更多还原