桥梁工程毕业设计外文翻译

精品文档 1欢迎下载 ReviewReview ofof assessmentassessment andand repairrepair ofof fire damagedfire damaged RCRC highwayhighway bridgesbridges AbstractAbstract This paper presents a review of the progress of the research and engineering practice of assessment and repair of fire damaged RC highway bridges based on which existing and pressing problems of the evaluation method are pointed out At last Prospect for the development of assessment and repair of fire damaged highway bridges is also proposed KeyKey wordswords fire damage assessment repair techniques RC structure bridge 1 1 PrefacePreface Fires can cause great structural damage to bridges and major disruption to highway operations These incidents stem primarily from vehicle accident often oil tanker fires bridges might also be damaged by fires in adjacent facilities and from other causes Quite a few of them though rarely happened lead to severe structural damage or collapse and casualty On June 2 2008 fire disaster broke out under the 18th span of Nanjing Yangtze River Bridge and lasted for approximate 75min During the fire s development and extinguishment the structure experienced the sharp rise and fall in temperature causing severe damage to fire stricken segments On April 29 2007 a gasoline tanker overturned on the connector from Interstate 8O to Interstate 880 in California The intense heat from the subsequent fuel spill and fire weakened the stee1 underbelly of the elevated roadway collapsing approximately 165 feet of this elevated roadway onto a 精品文档 2欢迎下载 section of I 880below On March 25 2004 Connecticut United States a tanker truck carrying fuel swerved to avoid a car and overturned dumping 8000 gallons of home heating oil onto the Howard Avenue overpass The consequent towering inferno melted the bridge structure and caused the southbound lanes to sag several feet Undocumented number of bridge fires occurring throughout the world each year cause varying degrees of disruption repair actions and maintenance cost Although fires caused damage to the bridge structures some bridges continue to function after proper repair and retrofit Still in some situations they have to be repaired for the cause of traffic pressure even though supposed to be dismantled and reconstructed However in other cases structures are severely damaged in the fire disaster and fail to function even after repair or the costs of repair and retrofit overweigh their reconstruction costs overwhelmingly even if they are repairable under which situation reconstruction serves as a preferable option Therefore in situ investigation and necessary tests and analyses should be conducted to make comprehensive assessment of the residual mechanical properties and working statuses after fire and to evaluate the degrees of damage of members and structures in reference to which decisions are made to determine whether Fire damaged structures should be repaired or dismantled and reconstructed Urgent need from engineering practice highlighted the necessity to understand the susceptibility and severity of these incidents as wel1 as to review available information on mitigation strategies damage assessments and repair techniques 2 2 ProgressProgress inin ResearchResearch andand EngineeringEngineering PracticePractice 2 12 1 ProcessesProcesses ofof AssessmentAssessment andand RepairRepair ofof FireFire damageddamaged 精品文档 3欢迎下载 BridgeBridge StructureStructure In China and most countries in the world most highway bridges are built in RC structure And the practice of the assessment and repair techniques of bridge structure after fire directly refer to that of RC structure which to date domestic and foreign scholars have made great amount of research on with their theories and practices being increasingly mature As for the assessment and repair of fire damaged reinforced concrete structures there are two mainstream assessment processes in world Countries including United States United Kingdom and Japan adopt the assessment process stipulated by The British Concrete Society This process grates the severity of fire damage of concrete structure into four degrees according to the deflection damage depth cracking width color and loading capacity variation of fire damaged structures and adopt four corresponding strategies including demolish strengthen after safety measures strengthen and strengthen in damaged segments to deal with them accordingly In general this process is a qualitative method and considered however not quantity enough In Chinese Mainland and Taiwan the prevailing as assessment and repair process of fire damaged incorporates following steps In comparison this process is more detailed 1 Conduct In situ inspections measurements and tests including color observation concrete observation degree of rebar exposure observation cracking measurement deflection measurement various destructive and nondestructive test methods as grounds for assessment of fire damaged structures In assessment of the post fire mechanical properties of fire damaged structures historical highest 精品文档 4欢迎下载 temperature and temperature distribution of structure during the fire serve as decisive factors The common methods to determine them incorporate petrographic analysis ultrasonic method Rebound method Ignition Loss method core test and color observation method 2 calculate to determine whether the fire damaged structure can meet the demand of strength and deflection under working loads after fire using mechanical properties of rebar and concrete before and after fire based on the historical highest and temperature distribution of structures obtained from step one There are two main methods to evaluate the post fire performance of fire damaged structures FEM method and Revised Classic Method 3 On the basis of test and calculation results obtained from step two take corresponding repair strategies and particular methods to strengthen the fire damaged structures 2 2 2 2 RepairRepair TechniquesTechniques For the repair of fire damaged bridge proper repair methods should be taken according to the degree and range of the structure s damage Meanwhile the safety and economy of the repair methods should be concerned with by avoiding destructing the original structure preserving the valuable structural members and minimizing unnecessary demolishment and reconstruction Common repair techniques are listed as follows 1 Fire damaged 1 Fire damaged concreteconcrete ReplacementReplacement The replacement of fire damaged concrete is the most common technique in damaged concrete repair If the concrete structure is damaged only within the concrete cover it is preferable to remove the fire damaged concrete from the structure making the rebar exposed and to make up the removed part by means of recasting or 精品文档 5欢迎下载 concrete spraying If the displacement of the structure exceeds the controlled value or the embedded rebar is buckled the damaged structure should be otherwise handled 2 CFRP 2 CFRP strengtheningstrengthening CFRP materials have strong tensile strength and elasticity as well as excellent workability and durability and are widely applied in engineering practice in recent years CFRP materials are used to boost the loading capacity by adhering them to the edge of tensile region to replace the reinforced rebar CFRP are especially suitable for the projects calling for boost of loading capacity while no extra weight is allowed 3 Structural 3 Structural membermember ReplacementReplacement For slab bridges and girder bridges the decks of the bridge are made of parallel girders or thick slabs On condition that part of structural member is severely damaged in the fire so that it s beyond repair or the repair cost over weigh a new one it is preferable to replace the damaged spans with new girders or slabs Though appears to be relatively high in cost this method serves as reliable and effective way in engineering practice 2 2 3 3 CaseCase StudyStudy ofof AssessmentAssessment andand RepairRepair TechniquesTechniques ofof fire fire damageddamaged bridgesbridges Some domestic and foreign scholars have conducted a series of studies on the inspection assessment and repair techniques of fire damaged bridges in the engineering practice by different assessment standards and processes on the case by case basis using a variety of field and laboratory evaluation methods including both destructive and 精品文档 6欢迎下载 nondestructive testing Literature employed visual inspection and material testing including compressive strength testing and petrographic analysis paste depth micro cracking color change on a fire damaged bridge based on which 1oad rating analysis was performed using reduced girder and deck sections Literature made qualitative safety evaluation on two fire damaged bridge structures using the rebound method core tests carbonization depth measurement concrete cover measurement deflection measurement and appearance observation Literature use the combination of ultrasonic method and rebound method to determine the historical highest temperature of structures in fire based on which stiffness and strength of two fire damaged structures are determined to make safety evaluations on them And then CFRP and structural adhensive are used to strengthen the fire damaged segments respectively Literature made a safety evaluation on a prestressed reinforced concrete slab bridge the fire directly stricken segments of which are severely spalled and carbonized with embedded rebars and prestressed strands exposed Its rubber isolators were also highly carbonized The researcher took the core tests and inferred that local segments of the slabs were severely damaged and the prestress had been lost Meanwhile the researcher conducted a series of dynamic tests on the damaged bridge and presumed that the variation of the comprehensive performance of the bridge structure after fire was insignificant in reference to the results of the dynamic tests The researcher proposed to replace the severely damaged slabs from the perspective of durability and safety Literature made the damage assessment and repair work on a fire damaged T shaped prestressed beam bridge The fire disaster was derived from the leakage of a oil tanker and then the burning oil 精品文档 7欢迎下载 was spread to the underbelly of the bridge Several boundary and secondary boundary girders are consequently damaged in the fire Judging by the fire duration color change and damage depth the researcher concluded that the fire damaged girders fell the category of severely damaged structures and cannot be repaired for the prestress loss and material degradation Therefore five spans of boundary and secondary boundary girders are dismantled and reconstructed LiteratureLiterature 1 Martha Davis P E Paul Tremel P E Alex Pedrego Bill williams Bridge Fire Assessment J Structure Magazine 2008 3O一 32 2 FENG Zhi nan CHEN Ai ping Inspection and Assessment of an Expressway Underpass Bridge After Fire Damage J World Bridges 2009 2 65 67 3 LI Yi XIANG Yi qiang WANG Jian jiang Damage Detection and Safety Assessment on Bridge Structure after Fire Accident J China Municipal Engineering 2006 5 26 27 4 LIU Qi wei WANG Feng XU Kai shun CHEN Xiao qiang Detection Evaluation and Repairing of Fire Damaged Bridge J Journal of Highway and Transportation Research and Development 2005 22 2 71 74 5 XI Yong Inspection and Evaluation of Fire Damaged Bridges J World Bridges 2007 4 62 65 6 SUN Da song MIAO Chang qing LI Zhi jun Examination and Evaluation of a Prestressed Concrete Slab Bridge after Fire J Municipal Engineering Technology 2007 25 3 246 248 精品文档 8欢迎下载 7 Zheng Jiguang W ang Xing Liu Zhonggu Analysis of Unforeseen Co nflagration Injury of Prestressed Concret Bridge Structure J Northern Communieations 2007 12 54 57 对火灾后钢筋混凝土公路桥梁的评估和修复 摘要 本文综述了对火灾后钢筋混凝土公路桥梁的研究进展 工程实践评估以 及修复 并在此基础上指出了现有的评估方法以及急需解决的问题 除此之外 还 对火灾后的公路桥梁的评估和修复提出了展望 关键字 火灾损害 评估 修复技术 钢筋混凝土结构 桥梁 1 前言 火灾能够对桥梁结构造成重大损害 并影响公路的正常使用功能 起因主 要源自车辆交通事故 通常是指油罐车 造成的火灾 周边设施着火或者其他 因素 都可能使桥梁结构发生损坏 尽管许多因素鲜有发生 但一旦产生就会 造成桥梁严重损坏并带来人员伤亡 2008 年 6 月 2 日 18 跨度的南京长江大桥发生了火灾 火灾持续了将近 75 分钟 伴随着大火持续燃烧和最终被扑灭 桥梁结构承受了急剧的温差变化 并给火灾影响到的桥段带来了严重的损坏 2007 年 4 月 29 日 一辆油罐车在 加利福尼亚州 80 号公路与 880 号公路交汇处发生侧翻 随后燃油泄漏 大火产 生的强热削弱了高架桥下不钢材的强度 最终高约 165 英尺高架路桥 I 880 段 发生倒塌 2004 年 3 月 25 日 美国 Connecticut 州 一辆携带燃油的油罐车 为了躲开与另外一辆车的相撞 左右转弯时发生倾倒 8000 加仑的家庭供暖燃 油被倾倒在 Howard Avenue 立交桥 随后漫天火海融化了桥梁结构 导致立交 精品文档 9欢迎下载 桥南行线降低了几英尺 世界各地还有许多未公布的桥梁火灾事故 都给桥梁造成了不同程度的损 坏 增加了修复和维护成本 虽然火灾给桥梁结构造成了损害 但经过适当的 维修和翻新 一些桥梁仍能继续使用 但在某些情况下 即使有些桥梁该被拆 除重建 但迫于交通压力 他们不得不在被维修之后就投入使用 然而 在某 些情况下 桥梁在火灾中损坏严重 即使被修复也无法正常使用 有时桥梁修 复翻新的费用压倒性地超过了重建的费用 在这种情况下 重建是一个较好的 选择 因此 应该对火灾后桥梁残余的力学性能和工作状态进行深入现场调查 做必要的检测分析 以准确检测出结构构件的破坏程度 之后来判定是该修复 被损毁的桥梁 还是将其拆了重建 实际工程的迫切需求 强调了很有必要去 了解桥梁对事故发生的敏感性 严重性 以及重新审查减灾战略 损害评定和 修复方法的相关信息 2 研究与工程实践的进展 2 1 桥梁结构受火灾损坏的评估以及修复进展 在世界上许多国家包括中国 大部分的公路桥是钢筋混凝土结构 实际当中 我们会直接参照混凝土结构来对遭受火灾之后的桥梁进行评估和修复 如此一来 到 目前为止 国内外的学者经过做了大量研究 这些理论和实践正日益成熟 至于对 火灾后的桥梁结构进行评估和修复 世界上有两种主流的评估流程 包括美国 英国和日本在内的许多国家都采用了由英国土木工程协会制定的 评估流程 参照偏斜的大小 损伤深度 裂缝宽 颜色以及损毁结构承载力的变化 评估流程将混凝土结构受火灾损坏程度划分为四个等级 并采取相应措施 包括 拆除 安全测量加固 加固受损段 对其进行处理 一般来说 这是一个定性的流 程 而不单单定量就足够了 中国大陆和台湾 现行的评估和修复过程采用如下步骤 经比较这种流程 更详细 1 进行现场调查 测量 颜色观察 具体观测钢筋暴露程度 开裂深度 测量 挠度检测以及各种破坏性和非破坏性的测试方法 是对火灾损坏结构的 评估依据 对火灾损毁的结构进行灾后力学性能分析 并对火灾过程中 结构 所达到的最高温度以及温度分布进行分析 常用的方法有岩相分析 超声波法 精品文档 10欢迎下载 核心测试和颜色观察 2 依据火灾之后工作荷载下的钢筋和混凝土力学性能 按照步骤一中火 灾前后结构所承受的最高温以及温度分布分析 通过计算来确定灾后结构是否 满足强度和挠度的要求 有两种主流的方法来判定结构遭受大火损坏之后其工 作性能 FEM 法和传统修复法 3 依据步骤二的结果统计和测试 采取相应的修复方案以及特定的方法 来加固受火灾损毁的结构 2 2 修复技术 修复火灾损毁的桥梁 应依据结构损坏的程度和范围来采取恰当的修复方 案 同时应该关注修复方法的安全性和经济型 尽量避免破坏原有结构 保留 有价值的构件 减少不必要的拆迁和重建 常规修复技术如下 1 更换火灾损坏的混凝土 用新混凝土代替火灾损坏的混凝土 是最常用的修复技术 如果仅仅是结 构的表面混凝土发生破坏 则优先采用去除损坏的混凝土 露出钢筋之后重新 浇筑或喷涂混凝土的方法 来代替被去除的部分 但如果结构的