目 录
: : : :
毕业设计任务书开 题 报 告文 献 综 述外 文 翻 译第一部分 第二部分 第三部分 第四部分
课题内容： 承担苏通大桥北引桥基础工程的施工组织设计和工程预算。设计内容包括： 1、施工条件分析； 2、施工总部署（包括施工进度安排）； 3、施工栈桥结构设计与施工、水上桩基施工方案的制定； 4、质量安全环保体系； 5、工程预算编制。 课题任务要求： 综合运用所学专业和专业基础知识对本课题进行设计，并辅以Project、造价管理系统、Midas等专业软件。通过本施工组织设计，全面了解和掌握施工组织设计的程序、内容，并综合运用所学知识解决实际工程问题，提高分析问题和解决工程实际问题的能力。设计方式以学生独立设计为主，教师知道为辅。 提交成果包括说明书和图纸两部分。 1、设计说明书：对所设计的内容，用文字和简图进行说明和总结，简明扼要；计算部分附必要的图示。 2、图纸一般采用A3图纸，不少于六张（施工工艺图、模板设计图、进度计划表、计划网络图、施工总平面布置图） 主要参考文献（由指导教师选定）： 1、《公路桥涵施工技术规范》（JTJ 041-2000） 2、《公路工程质量检验评定标准》（JTJ 071-98） 3、范立础主编. 《桥梁工程》.北京：人民交通出版社，2001 4、黄绳武主编. 《桥梁施工及组织管理》.北京：人民交通出版社，2000 5、周水兴、何兆益、邹毅松等主编，《路桥施工计算手册》.北京：人民交通出版社，2001 6、陈伟、李明主编.《桥梁施工临时结构设计》.北京：中国铁道出版社，2002 7、《桥涵施工手册》 8、公路施工手册.《桥涵》（上、下册）.北京：人民交通出版社，2000 9、《公路工程预算定额》（上、下册），2007 10、《公路工程施工安全技术规程》（JTJ 076-95） 11、《港口工程桩基规范》（JTJ 254-98） 12、《港口工程钢筋钩设计规范》（JTJ 283-99） 13、《港口工程荷载规范》（JTJ 215-98） 14、中交第一公路工程局有限公司.《公路工程施工工艺规范》.北京：人民交通出版社，2007 同组设计者 学生完成毕业设计（论文）工作进度计划表
工 作 进 度 日 程 安 排 序号 毕业设计（论文）工作任务 周次 1 2.5 5.5 0.5 1.5 1 1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 1 2 3 4 5 6 7 8 9 10 收集资料及熟悉图纸 工程量计算及施工总布署 施工方案 施工组织 工程预算 整理、装订设计成果 答辩 注：1. 此表由指导教师填写。
2. 此表每个学生一份，作为毕业设计（论文）检查工作进度之依据； 3. 进度安排请用“—”在相应位置画出。
毕业设计（论文）阶段工作情况检查表
时间 内容 组织纪律 第一阶段 完成任务情况 组织纪律 第二阶段 完成任务情况 组织纪律 第三阶段 完成任务情况 检查 教师 签字 注：1. 此表应由教师认真填写；
2. “组织纪律”一栏根据学生具体执行情况如实填写；
3. “完成任务情况”一栏按学生是否按进度保质保量完成任务的情况填写；
4. 对违纪和不能按时完成任务者，指导教师可根据情节轻重对该生提出警告或不能参加答辩的建议。
情况签字 日期 签字 日期 签字 日期
毕业设计（论文）
开题报告
题 目 苏通大桥北引桥——
施工栈桥基础工程施工组织设计 专 业 班 级 学 生 指导教师
开题报告
一、选题目的的理论价值和现实意义
作为一名工科毕业的大学生，施工技术专业知识是必不可少的，同时，施工组织与管理知识也同样很重要。通过毕业设计，进一步巩固和提高已学过的基本理论和专业知识，增强运用已学知识解决实际问题的能力；进一步掌握施工组织的基本步骤，懂得如何对实际工程进行施工组织设计和掌握具体的施工技术；初步掌握施工计划网络图的绘制方法及时性其优化原理；初步掌握工种预算的理论和方法；培养毕业生独立解决问题的能力，尽快适应以后所从事的工作，为将来走上工作岗位奠定坚实的基础。
苏通大桥位是我国建桥史上工程规模最大、综合建设条件最复杂的特大型桥梁工程。建设苏通大桥对完善国家和江苏省干线公路网、促进区域均衡发展以及沿江整体开发，改善长江安全航运条件、缓解过江交通压力、保证航运安全等具有十分重要的意义。
二、本课题在国内外的研究状况及发展趋势
苏通大桥前期工作开始于1991年，经历了规划、预可、工可、初设和施工图设计等阶段。从1991年进行规划研究，至2003年6月开工，历时12年。1998年江苏省上报了苏通大桥项目建议书，1999年4月，交通部组织专家对苏通大桥项目建议书进行了行业评审；1999年9月，国家计委组织专家对项目建议书进行了评估；2001年6月，国家计委以“计基础[2001]1089号”文批准苏通大桥项目建议书；2001年12月，江苏省和交通部联合在南京主持召开了苏通大桥国际技术研讨会。2002年2月，受国家计委委托，中国国际工程咨询公司组织专家对工可报告进行了评估。2002年4月，评估报告上报国家计委。2002年11月，交通部分别组织有关专家对苏通大桥基础设计资料、结构设计参数、设计方案等进行了现场调研和审查；2003年3月，交通部以“交公路发[2003]95号”文批复了苏通大桥初步设计；2003年6月，经交通部同意，同时江苏省发展计划委员会以“苏计投资函（2003）123号”转达国家发展和改革委员会意见，同意苏通大桥控制工程先行开工建设。
苏通大桥不仅规模宏大，在斜拉桥几何尺度方面创造四项世界第一，而且在技术方面极具挑战性，难度非常大，是从设计到施工、科研和管理等全方位的超越。可以说，它比国内以往任何一座桥梁遇到的难题更多、建设更复杂，因此它代表了目前中国乃至世界建桥技术的最前沿。
三、研究重点
作为本次设计的苏通大桥北引桥部分，由陆地和水上两部分组成。主要施工项目有水上钻孔灌注桩、水上承台、墩台、箱梁以及钢栈桥和施工平台的施工。本设计的重点和难点就在于钻孔灌注桩和水上承台的施工。在施工中分别采用了回旋钻机泥浆护壁水下灌注混凝土和钢吊箱的施工方法。
四、主要参考文献
[1] 《公路桥涵施工技术规范》(JTJ041-2000)。
[2] 周永兴，《路桥施工计算手册》[M]，北京：人民交通出版社，2001。 [3] 丛培经，《工程项目管理》[M]，北京：中国建筑工业出版社，2003。 [4] 范立础,《桥梁工程》[M]，北京：人民交通出版社，2001。
[5] 黄绳武，《桥梁施工及组织管理》[M]，北京：人民交通出版社，2000。
五、指导教师意见
指导教师： 六、学院毕业设计（论文）指导小组意见
负责人：
文献综述
苏通大桥主要由北岸接线工程、跨江大桥工程和南岸接线工程三部分组成。作为本次设计的B1合同段属于北岸接线工程，位于北岸浅滩区，30m跨段位于陆上，50跨段位于水深较浅的岸边。因此施工的重点也是难点就在于钻孔灌注桩以及现浇预应力混凝土箱梁的施工。
钻孔灌注桩目前在沿海地基处理中应用十分广泛，但因属隐蔽工程，成桩后质量检查比较困难，且由于软土的特殊性质，经常会出现一些质量问题。在查阅了大量文献及期刊论文后,现对其在施工过程中经常遇到的问题和相应的防治措施做简要阐述。
钻孔灌注桩施工过程：施工准备→泥浆制备→打设护筒→钻机就位→钻进成孔→清孔并检查成孔质量→下放钢筋笼→下导管→二次清孔→水下混凝土灌注→护筒回收→检查质量。
在施工中经常遇到的问题和相应的防治措施： 孔口高程及钻孔深度的误差
孔口高程的误差：孔口高程的误差主要有两方面，一是由于地质勘探完成后场地再次回填，计算孔口高程时疏忽引起的误差。二是由于施工场地在施工过程中废渣的堆积，地面不断升高，孔口高程发生变化造成的误差。其对策是认真校核原始水准点和各孔口的绝对高程，每根桩开孔前复测一次桩位孔口高程。
钻孔深度的误差：有些工程在场地回填平整前就进行工程地质勘探，地面高程较低，当工程地质勘探采用相对高程时，施工应把高程换算一致，避免出现钻孔深度的误差。另外，孔深测量应采用丈量钻杆的方法，取钻头的2/3长度处作为孔底终孔界面，不宜采用测绳测定孔深。钻孔的终孔标准应以桩端进入持力层深度为准，不宜以固定孔深的方式终孔。因此，钻孔到达桩端持力层后应及时取样鉴定，确定钻孔是否进入桩端持力层。 孔径误差
孔径误差主要是由于工人疏忽用错其他规格的钻头，或因钻头陈旧，磨损后直径偏小所致。每根桩开孔时，合同双方的技术人员应验证钻头规格，实行签证手续。 钻孔垂直度不符合规范要求
造成钻孔垂直度不符合规范要求的主要原因如下：场地平整度和密实度差，钻机安装不平整或钻进过程发生不均匀沉降，导致钻孔偏斜；钻杆弯曲、钻杆接头间隙太大，造成钻孔偏斜；钻头翼板磨损不一，钻头受力不均，造成钻头偏离方向；钻进遇软硬土层交界面或倾斜岩面时，钻压过高使钻头受力不均，造成钻头偏离方向。
主要技术措施为：压实、平整施工场地；安装钻机时应严格检查钻进的平整度和主动钻杆的垂直度，钻进过程应定时检查主动钻杆的垂直度，发现偏差应立即调整；定期检查钻头、钻杆、钻杆接头，发现问题及时维修或更换；在软硬土层交界面或倾斜岩面处钻进，应低速低钻压钻进。发现钻孔偏斜，应及时回填粘土，冲平后再低速低钻压钻进；在复杂地层钻进，必要时在钻杆上加设扶整器。 钻孔塌孔
钻孔灌注桩的塌孔与缩径主要是地层复杂、钻进进尺过快、护壁泥浆性能差、成孔后放置时间过长没有灌注砼等原因所造成。钻孔灌注桩穿过较厚的砂层、砾石层时，成孔速度应控制在2米/小时以内，泥浆性能主要控制其密度为1.3~1.4g/cm3、粘度为20~30s、含砂率≤6％，若孔内自然造浆不能满足以上要求时，可采用加粘土粉、烧碱、木质素的方法，改善泥浆的性能，通过对泥浆的除砂处理，可控制泥浆的密度和含砂率。没有特殊原因，钢筋笼安装后应立即灌注砼。 桩端持力层判别错误
孔底沉渣过厚或开灌前孔内泥浆含砂量过大
孔底沉渣过厚除清孔泥浆质量差，清孔无法达到设计要求外，还有测量方法不当造成误判。要准确测量孔底沉渣厚度，首先需准确测量桩的终孔深度，桩的终孔深度应采用丈量钻杆长度的方法测定，取孔内钻杆长度＋钻头长度，钻头长度取至钻尖的2/3处。
灌注砼过程钢筋笼上浮
引起灌注砼过程钢筋笼上浮的原因主要有如下三方面：砼初凝和终凝时间太短，使孔内砼过早结块，当砼面上升至钢筋笼底时，砼结块托起钢筋笼；清孔时孔内泥浆悬浮的砂粒太多，砼灌注过程中砂粒回沉在砼面上，形成较密实的砂层，并随孔内砼逐渐升高，当砂层上升至钢筋笼底部时便托起钢筋笼；砼灌注至钢筋笼底部时，灌注速度太快，造成钢筋笼上浮。
若发生钢筋笼上浮，应立即查明原因，采取相应措施，防止事故重复出现。 桩身砼夹渣或断桩
原因主要有如下四方面：初灌砼量不够，造成初灌后埋管深度太小或导管根本就没有入砼内；砼灌注过程拔管长度控制不准，导管拔出砼面；砼初凝和终凝时间太短，或灌注时间太长，使砼上部结块，造成桩身砼夹渣；清孔时孔内泥浆悬浮的砂粒太多，砼灌注过程中砂粒回沉在砼面上，形成沉积砂层，阻碍砼的正常上升，当砼冲破沉积砂层时，部分砂粒及浮渣被包入砼内。严重时可能造成堵管事故，导致砼灌注中断。 导管的埋管深度宜控制在2～6米之间，若灌注顺利，孔口泥浆返出正常，则可
适当增大埋管深度，以提高灌注速度，缩短单桩的砼灌注时间。砼灌注过程拔管应有专人负责指挥，并分别采用理论灌入量计算孔内砼面和重锤实测孔内砼面，取两者的低值来控制拔管长度，确保导管的埋管深度≥2米。单桩砼灌注时间宜控制在1.5倍砼初凝时间内。
参考文献：
[1] 《公路桥涵施工技术规范》(JTJ041-2000)。
[2] 周永兴，《路桥施工计算手册》[M]，北京：人民交通出版社，2001。 [3] 丛培经，《工程项目管理》[M]，北京：中国建筑工业出版社，2003。 [4] 范立础,《桥梁工程》[M]，北京：人民交通出版社，2001。
[5] 黄绳武，《桥梁施工及组织管理》[M]，北京：人民交通出版社，2000。
[6] 赵海津，许晶.钻孔灌注桩施工中的质量事故原因及预防措施[J].华章，2009，(11). [7] 张秀丽.浅谈钻孔灌注桩的施工[J].黑龙江科技信息，2008，(24). [8] 张东平.浅议钻孔灌注桩质量控制[J].南方金属，2007，(4).
[9] Seed H B, Reese L C. The Action of Soft Clay along Friction Piles .Transactions, ASCE,
1957,122, 122 :731~754 .
[10] Boulon M, Nova R. Modeling of soil structure interface behavior - a comparison
between elastoplastic and rate-type laws .Computers and Geotechnics, 1990,91, 9(1) :21-46 .
斜拉桥以及桥梁的施工技术
在过去十年里，斜拉桥被世界各地广泛应用，尤其是在西欧。在现代桥梁工程中，斜拉体系的更新，则是由于欧洲尤其是德国的桥梁工程师在战后由于材料的短缺为获得最佳的结构性能而兴起的。
斜拉桥的结构系统是由正交异性桥面和由拉索支撑的连续加劲梁组成，即斜索穿过或直接锚固在索塔上。
利用拉索来支撑桥跨绝不是一种新技术，很早以前就有关于这种结构的实测记载了。不幸的是，由于没有充分理解其受力状态和用以形成斜拉索线支撑的那些材料，如拉杆、拉索都不合适，因此这种体系很少有成功的先例，用这种方法制作的拉索没有充分拉紧，而处于松弛状态的斜拉索的拉力在远未达到设计值时，桥面就出现了很大的变形。
随着高强钢丝、正交异性板的引进，焊接技术的发展和结构分析的进步，斜拉桥体系直到近来才被广泛成功地应用。电子计算机技术的发展和应用对解决高次超静定体系问题及其三维性能的精确静力分析开辟了新的无限天地。
斜拉桥是一种空间结构，主要由钢梁、钢或混凝土桥面系和支撑部分包括处于受压状态的塔和处于受拉状态的斜拉索组成。就结构性能而言，斜拉桥介于梁桥和悬索桥之间。
这种体系的主要结构特点是利用加劲和预应力或后张拉索的联合作用，拉索从塔顶一直延伸到钢梁锚固点。斜拉索的水平分力主要由主梁承担，不需要大的锚固装置，因此，下部结构是非常经济的。
正交体系的引进导致几种新型下部结构的产生，新型结构不需要任何外加材料就能承受缆索的水平推力，即便对大跨径桥梁也是如此。
在传统的上部结构中，桥面板、纵梁、横梁和主梁被认为是独立受力的，这类上部结构不适用于斜拉桥。但是，在旧的体系中，正交异性板和大型断面的加劲刚板不仅起到主梁及横梁上弦杆的作用，同时也起到抵抗风撑的水平梁桥的作用。事实上，在正交异性体系中道路的所有组成部分和上部结构的次要部分都参与了桥梁主体系统的受力，这使得主梁梁高减少，并节约了用钢量。
这种结构的另一特征是不管桥上的荷载情况如何，桥的几何形状总是不变，所有拉索总是处于受拉状态 ，因此斜拉桥可用相对轻巧灵便的材料——缆索来修建。
这种三维桥的重要特征是横向结构部分完全参与纵向主体结构的受力。这就意味着结构的抗弯惯性矩大大增加，从而允许梁高减小并能节省钢材。
正交异性体系保证了桥面板在索塔处和中心主跨处的连续性。多跨桥上部结构的连续性非常重要，对设计良好的斜拉桥来说尤为重要。
斜拉桥在公路桥领域的应用填补了板桥和悬索桥之间的空白。在中等跨度的情况下正交异性板梁要比其它体系优越。但是，对于大跨径的桥梁则需要很大的梁高。斜拉桥解决了这个问题，因为它是一个包括正交异性板和连续梁组合的结构体系。
斜拉桥的出现确实是桥梁建筑上一个具有开拓性的发展，现有的斜拉桥是钢结构的杰作。造型优美、结构明快。完全不需要外加装饰。这是因为斜拉桥的设计不仅有经济、实用和技术上的要求，在很大程度上还要考虑美学和建筑学的要求。现代斜拉桥设计的目标之一就是与环境融为一体，满足美学要求。
这些桥梁确实是现代社会的代表产物，是现代工程科学在其自身的规律下不断发展前进、且已被20世纪的工程师们赋予其实质的产物。
如何建一座桥，包括斜拉桥在内，主要取决于现场的情况。包括材料的成本、可供使用的设备，所允许的施工时间和环境限制。由于所有这些都会随着选址和时间的不同而不同，所以对于一个指定的结构，其最好的施工方法也会不同。
顶推法
在这种施工方法中，利用液压千斤顶和卷扬机将桥面推过各桥跨。预应力后张预制桥面段、钢梁和箱梁是已建好了的。尽管跨度更大的桥梁通过安装临时支撑的方法已经建起来，但为了避免过大的挠曲和悬臂应力，跨度通常限制在50～60m。这种施工方法最适合于修建跨度在300 ～ 600m范围内的多跨桥，但是利用这样的方法已经建成了比这更短或更长的桥梁。不幸的是，这种经济的施工方法只有在桥面的水平和垂直线形都是直线或者要有稳定不变的半径时才适用。如果顶推梁有较小的下坡（4%～5%），就必须安装制动系统，以防止滑动失控，此时在约束墩上应设置大型支撑架。
桥梁推进要求有认真的测量和对桥面挠曲进行持续精确的检查。桥面的前端由一个铝或钢导梁形成，在桥墩上起着前导作用。使用特制的聚四氟烯或铬镍的钢板支座可将滑动摩擦力减到其重量的5％，这样，就可以使带有支柱的细长桥墩免遭断裂或其他损坏。这些支柱还可以支撑临时摩擦支座，也有助于控制导梁。
在预制施工时，是把理想的节段浇筑在靠近桥台的台座上，然后由导轨将它运到后张台座上，这当中的运送距离应该保持最小。通常，节段是浇筑在相邻的已经建好了的节段的端面上，这样就可以保证用环氧树脂将它粘贴到位。如果不采用这种程序，就应该在节段与节段之间留出约500mm的缝隙，在这些缝里加钢筋并在后张拉开之前浇混凝土。一般是将所有的段压在一起形成一个完整的结构，但是，当路堤的入口或
空间不够时，就有必要间歇地推进桥面，这样才可以逐渐增加梁段。相应的预应力配置，不管是临时性的还是永久性的，都要有更复杂和更仔细的计算。
桥顶推技术的主要优势是节约脚手架，特别是对于那些高架桥面的桥，节段也可以使用高效率的设备在受保护的环境下制造或预制。就混凝土节段而言，每周可架设两个节段（一般长度为10～30m，重约300～400t）并在后张拉之后，根据绞车/起重机的情况，每天顶推20m左右。
平衡悬臂施工法
箱形截面和预应力混凝土的发展使人们可以在脚手架上进行现场安装和浇筑短节段，建造与路面等宽的梁。接着，通过不用脚手架而用已建好了的梁的一部分来稳固悬臂段，这一举措改善了施工方法。
在所举的这一简单例子里，桥由长度比1:1:2的三个跨构成。首先，桥台和桥墩与桥的上部结构分开建造。每个桥墩上面的桥段可以现场浇筑或安装预制段，然后通过在其两端同时增加节段来建造桥面。不过，在两端必须同时增加理想节段通常使不现实的，而且附加段的重量、风力、施工平台和材料也会引起不平衡。当悬臂到达了两端桥台和中跨跨中时，便可在另一桥墩上进行施工了，桥面的剩余部分也以同样的方法来完成。最后，用一个合拢段将两个悬臂在中心连接，从而形成一个单独的跨。合拢段通常是现场浇筑的。
该程序在开始时要求墩柱顶部甚至其左右两面的使用节段，按常规方式现浇或预制安装，并在预应力筋穿束并后张时对其进行临时支撑。而其它的节段，是利用后张法并进行孔道灌浆一对对安装就位的。在这一阶段只有上翼梁和梁腹的悬臂钢筋束是受拉的。在合拢段浇筑到位后，对通长钢筋施加预应力，最后在两个半跨中间留下的缝隙要足够宽，使得千斤顶装置可以安进去。当每个悬臂梁都完工并且合拢段也安装好了之后，便在桥跨中心将通长钢筋对称锚固，使它可以承受叠加荷载、活载、恒载内力重分布和悬臂预应力。
早期桥梁是按自由悬臂原则来设计的，它要求桥中心有个伸缩缝。不幸的是，沉降、变形、混凝土徐变和预应力松弛会使两半桥跨产生挠曲，从而破坏桥的外观，使驾驶人员产生不舒适感。这种接缝引起的后果和设计上的困难，促使设计人员选择使用连续的连接方法，使得荷载更均匀和变形减小。自然的伸缩缝通过桥台处滑动支座来实现，对于多跨长桥，则隔500m设一接头来实现。
先进施工方法的特别要求:有三个方面是工程队伍和施工队伍必须考虑的：
1、 施工过程的应力分析：因为此时桥的荷载和支撑跟竣工之后的不同，为了保证结构的安全，必须计算每个施工期的荷载。为此，必须使用实际施工荷载，并
通知所有现场工作人员其荷载的极限。风力和气温对各施工期都很有影响。
2、 反拱：为了使所建的桥的标高准确，每个施工期都必须计算桥梁所要求的预拱度。对混凝土徐变给予应有的考虑。虽然这类计算很复杂，但计算机的应用已使它简单化了。
3、 质量控制：这对于任何一种施工方法都很重要，对复杂的施工方法尤其重要。混凝土养护、后张拉、伸缩缝预留等都不利于一个成功的结构。现场工作人员必须了解，在后张拉、拆模、脚手架拆除、架设和其它的操作时所要求的混凝土的最小强度。
一般来说，这些先进的施工方法比传统的脚手架施工方法要有更多的管理工作，但节约的成本相当可观。
桥梁的修复
桥梁的修理和维护与桥梁修复之间的分界线有时是很模糊的。通常的区别隐含于把桥恢复到满意的状况所需维修的程度。维修指在现有条件下修理构件，修复通常是要延长现有桥的使用寿命。几个研究项目包括如何提高桥的承载能力和对功能不完善的桥的修复的研究。
修复可以采用几种修复工序中的任一种形式。工作可能包括桥面的更换和小修，或者包括纠正沉降问题，加固或更换危险构件，更换支座，加宽和纠正线形，或改善排水等。
一、 桥面更换
桥最常见的修复是更换桥面或磨损的部分。最普遍的磨损是氯离子渗入混凝土中并腐蚀钢筋造成的。桥面放置的防冻化学物是氯离子的来源。桥面修复的类型和程度很大程度上取决于氯化物含量和破坏的桥面所占的百分比例。在钢筋布置层面每立方码混凝土氯化物含量小于1磅时，采用防水膜或低塌落度混凝土修补每立方码氯化物含量大于2磅，也就是说通常所称的临界浓度，大多数的公路机构除去上层钢筋底部以上污染的混凝土，给钢筋喷砂，再给钢筋涂上一层环氧保护材料，然后再浇上新的混凝土。
对于氯化物破坏面较大的桥面，有时候采用阴极保护和环氧灌浆的方法。现在一些政府机构使用阴极保护已有一段时间，用于钢筋腐蚀严重的桥面的关键部位。如果40％的桥面遭受破坏，一般建议全部更换桥面。在一些情况中，临时修补和坑洼修补用在破坏较严重的桥面，直到钢筋腐蚀或者混凝土磨损厉害，致使其结构不能保障规定的荷载安全通过。通常的，桥面更换结合给上层钢筋涂保护材料、设防水层或者低塌落度混凝土面层来保护桥面不过早受氯化物侵蚀。
二、 主梁更换或加固
根据需要修理的类型和程度，混凝土主梁的修补可采用不同的方法。某些表面修补用来保护裸露的钢筋，但常规下，把一块一块的混凝土粘起来是不成功的。环氧压浆能成功地用来保护钢筋，尤其是预应力钢筋束避免受潮。然而，这些方法只该用在重新分析结构，并考虑到由磨损引起的其他任何缺陷以后才采用。既然结构只是恢复至原来的状况，并且其过程减缓了磨损以及可能（或许不能）延长其使用寿命，这种修复只能被认为是维修。
其他混凝土构件的修复包括用螺栓栓起来防止应力集中，应力集中可能导致疲劳破坏。如果损伤或磨损导致钢构件失效，通常就可以更换它们。更换桁架中的构件是通常之举。钢梁桥也可以通过复合作用得到加强。这个加强过程是通过在混凝土桥面和钢梁之间设置一个剪力联系完成的。在老化桥面的更换过程中，螺栓和梁焊在一起来为复合作用传送必要的剪力。完成这样的剪力联系的其他方法有：在桥面钻孔来连接螺栓，并在梁和桥面之间作环氧压浆。为了获得连续效应，把简支梁联结起来，用来加固已有的钢桥。如前所述，这样的加固要求由经验丰富的工程师进行修复和更新设计。
三、 减少恒载
另一种容易实现的增加承载能力的方法是减少恒载。在许多年代较早的梁中，沥青面层一直累积到其恒载很大的程度。在其他情况下，整个桥面可能被除去，更换上更轻质的桥面材料。
用于旧桥换新面的三种材料是：（1）开口的网格钢板；（2）冷轧波纹金属板；（3）胶合木板。开口的网格钢板的优势在于雨和雪可以通过，并免去了对桥面排水系统的需要，但当其潮湿或被冰雪覆盖时，钢板变得很滑。波纹金属板放在已有的纵梁上和一些辅助的轻型支撑梁上。这里，必须有适当的排水系统；否则，波纹金属板就会被逐渐腐蚀。胶木薄板或预应力木板是最近的一个新发明。预制的板条通常夹嵌或栓在已有的梁上。一种合适的薄板条，由于不受控制冰雪冻害的化学物质的侵蚀，因而显出其优势。
四、几何外形
桥梁的修复可能包括以改变竖向净空、加宽结构或改善水平或竖直向线形的方式来优化几何外形。
桥梁破坏的一种普遍形式是由于竖向净空限制引起的车辆碰撞。当一条路线上有一两座桥的竖直净空比其他结构少很多时，这种破坏相当常见，桁架常常归入这种情形。
通过减少门架横撑的厚度或降低底层体系以增加竖直净空，这不失为改造的成功方法，较薄的桥面系也可以提供额外的净空。
可抬高立交桥或让公路在立体交叉口的路面降低。两种方法都被公路部门用于提高竖向净空。美国不同的公路机构已使用了许多种道路加宽的方法。Hackensack河大桥是通过强化中线对称来加宽的。John Harris大桥则全部在一侧加宽。加宽结构以满足今天交通量的最低标准，可以延长桥的使用寿命。这种过程在许多大桥上成为合理的例行程序，包括除去人行道和边石，加宽桥墩和桥台，添加新的纵梁和桥面。
五、机械缺陷
与结构收缩、膨胀相关的支座，伸缩缝，托架等类似的设备需经常修复。这些设备通常因为腐蚀或杂物堆积而失去功效。通常，其修复包括清洁设备的位置。明尼苏达州开创了一个移动冻结的支座、喷砂或清洗设备的新程序，并且提供了油脂填充物，使支座能得到定期的检修。
水和氯化物溶液通过桥面伸缩缝渗入到梁或墩帽上，这是经常引起桥梁腐蚀的主要问题。经常更换接缝密封条可改善这种状况。安装或维修（如果已有的话）排水汇集系统，可以把开口接头流出的水排到远离支座或托架的地方。桥面排水孔可用来控制排水，使水从桥面流走。
六、安全性和适用性
桥上有些地方的维修是针对安全性的，包括失效栏杆的更换、桥栏杆或护栏根部的改造等。在桁架、桥墩或分道用角区域两端的危险地方用减震器更换护栏栏杆和保护设施，可获得桥梁安全性的恢复。校正道路线形对桥的安全记录有很大影响。
道路的适用性可用几种方法来改善。在桥的端头维修引道混凝土路面的沉降可提高许多结构的行车质量。桥面坑洼和打滑部分的修复可提高桥的安全性和行车舒适感。
桥梁检查现在被认为是道路工作程序的一个重要部分。如果要保持程序的有效性，就必须通过一个连续的维护和修复程序来处理排水不畅、老化和其他缺陷。如果给合理的维护和维修程序提供资金并贯彻执行，那么就能很快地避免公路基础设施建设中的巨大投资。
Cable-stayed bridges and Construction techniques
During the past decade cable-stayed bridges have found wide application, especially in Western Europe, and to a lesser extent in other parts of the world. The renewal of the cable-stayed systems in modern bridge engineering was due to the tendency of bridge in Europe, primarily Germany, to obtain optimum structural performance from material which was in short supply during the post-war years.
Cable-stayed bridges are constructed along a structural system which comprises an orthotropic deck and continuous girders which are supported by stays, i.e. inclined cables passing over or attached to towers located at the main piers.
The idea of using cables to support bridge spans is by no means new, and a number of examples of this type of construction were recorded a long time ago. Unfortunately, the system in general met with little success, due to the fact that the statics were not fully understood and that unsuitable materials such as bars and chains were used to form the inclined supports or stays. Stays made in this manner could not be fully tensioned and in a slack condition allowed large deformations of the deck before they could they could participate in taking the tensile loads for which they were intended.
Wide and successful application of cable-stayed systems was realized only realized only recently, with the introduction of high-strength steels, orthotropic type decks, development of welding techniques and progress in structural analysis. The development and application of electronic computers opened up new and practically unlimited possibilities for the exact solution of these highly statically indeterminate systems and for precise statical analysis of their three-dimensional performance.
Cable-stayed bridges present a space system, consisting of stiffening girders, steel or concrete decks and supporting parts as towers acting in compression and inclined cables in tension. By their structural behavior cable-stayed systems occupy a middle position between the girder type and suspension type bridges.
The main structural characteristics of this system is the integral action of the stiffening girders and prestressed or post-tensioned inclined cables, which run from the tops down to the anchor points at the stiffening girders. Horizontal compressive forces due to the cable action are taken by the girders and no massive anchorages are required. The substructure, therefore, is very economical.
Introduction of the orthotropic system has resulted in the creation of new types of substructure which can easily carry the horizontal thrust of stay cables with almost no additional material, even for very long spans.
In old types of conventional superstructures, the slab, stringers, floor beams and main girders were considered as acting independently. Such superstructures were not suitable for cable-stayed bridges. With the orthotropic type deck, however, the stiffened pate with its large cross-sectional area acts not only as the horizontal plate girder against wind bracings used in old systems. In fact, in orthotropic systems, all elements of the roadway and secondly parts of the superstructure participate in the work of the main bridge system. This results in reduction of the depth of the girders and economy in the steel.
Another structural characteristics of this system is that it is geometrically unchangeable under any load position on the bridge, and all cables are always in a state of tension. This characteristics of the cable-stayed systems permits them to be built from relatively light flexible elements _ cables.
The important characteristic of such a three-dimensional bridge is the full participation of the transverse structural parts in the work of the main structure in the longitudinal direction. This means a considerable increase in the moment of inertia of the construction, which permits a reduction of the depth of the girders and a consequent saving in steel.
The orthotropic system provides the continuity of the deck structure at the towers and in the center of the main span. The continuity of the bridge superstructure over many spans has many advantages and is actually for a good cable-stayed bridge.
Considering the range of applications in the domain of highway bridges, cable-stayed bridges fill the gap that existed between deck type and suspension bridges. Orthotropic deck plate girders showed superiority over other systems in the case of medium spans. For long spans, however, they required considerable girder depth. The cable-stayed bridge provides a solution to this problem, based on a structural system comprising an orthotropic plate deck and a continuous girder.
The introduction of the cable-stayed system is a true pioneering development in bridge architecture. Existing cable-stayed bridges are masterpieces of steel construction. They are pleasing in outline, clean in their anatomical conception and totally free of meaningless ornamentation. This is because the design of cable-stayed bridges was governed not only by financial, practical and technical requirements, but also, to a great extent, by aesthetic and architectural considerations. In the design of modern cable-stayed bridges, one objective is to produce an aesthetically appeasing bridge which blends with its surroundings.
These bridges are truly representative of modern times. They are the products of engineering science, which is continuously advancing in accordance with its own laws and has been given form and substance by twentieth century engineers.
The decision of how a bridge, including a cable-stayed bridge, should be built depends mainly on local conditions. These include cost of material, available equipment, allowable construction time and environmental restrictions. Since all these vary with location and time, the best construction technique for a given structure may also vary.
Incremental launching or push-out method
In this form of construction the deck is pushed across the span with hydraulic rams or winches. Decks of prestressed post-tensioned precast segments, steel or box girders have been erected. Usually spans are limited to 50-60m to avoid excessive deflection and cantilever stresses, although greater distances have been bridged by installing temporary support towers. Typically the method is most appropriate for long, multi-span bridges in the range 300-600m, but, much shorter and longer bridges have been constructed. Unfortunately, this very economical mode of construction can only be applied when radius. Where pushing involves a small downward grade (4%-5%), then a braking system should be installed to prevent the deck slipping away uncontrolled and heavy bracing is thus needed at the restraining piers.
Bridge launching demands very careful surveying and setting out with continuous and precise checks made of deflections. A light aluminum or steel launching nose forms the deck to provide guidance over the pier. Special Teflon or chrome-nickel steel plate bearings are
used to reduce sliding friction to about 5% of the weight, thus slender piers would normally be supplemented with braced columns to avoid cracking and other damage. These columns would generally also support the temporary friction bearings and help steer the nose.
In the case of precast construction, ideal segments should be cast on beds near the abutmentsand transferred by rail to the post-tensioning bed, the actual transport distance obviously being kept to the minimum. Usually a segment is cast against the face of the previously concreted unit to ensure a good fit when finally glued in place with an epoxy resin. If this procedure is not adopted, gaps of approximately 500mm should be left between segment is cast against the face of the previously concreted before post-tensioning begins. Generally all the segments are stressed together to form a complete unit, but for the temporary and permanent conditions, would be more complicated and careful calculations needed at all positions.
The principal advantage of the bridge-launching technique is the saving in the falsework, especially for high decks. Segments can also be fabricated or precast in a protected environment using highly productive equipment. For concrete segments, typically two segments are laid each week (usually 10-30m in length and perhaps 300 to 400 tons in weight ) and after post-tensioning incrementally launched at about 20m per day depending upon the winching/jacking equipment.
Balanced cantilever construction
Developments in box section and prestressed concrete led to short segments being assembled or cast place on falsework to form a beam of full roadway width. Subsequently the method was refined virtually to eliminate the falsework by using a previously constructed section of the beam to provide the fixing for a subsequently cantilevered section. The principle is demonstrated step-by-step in the example shown in Fig. 19-2.
In the simple case illustrated, the bridge consists of three spans in the ratio 1:1:2. first the abutments and piers are constructed independently from the bridge superstructure. The segment immediately above each pier is then either cast in situ or placed as a precast unit. The deck is subsequently formed by adding sectongs symmetrically either side.
Ideal sections on either side should be placed simultaneously but this is usually impractical and some imbalance will result both the abutment and center span, work can begin from the other pier, and the reminder of the deck can be completed in a similar manner. Finally the two individual cantilevers are linked at the center by a key segment to form a single span. The key is normally cast in situ.
The procedure initially requires the first sections above the column and perhaps one or two on each side to be erected conventionally either in situ or precast and temporarily supported while steel tendons are threaded and post-tensioned. Subsequent pairs of sections are added and held in place by post-tensioning followed by grouting of the ducts. During this phase, only the cantilever tendons in the upper flange and webs are tensioned. Continuity tendons are stressed after the key section has been cast in place. The final gap left between the two half spans should be wide enough to enable the jacking equipment to be inserted. When the individual cantilevers are completed and the key section inserted, the superimposed loads, live loads, redistribution of dead loads and cantilever prestressing forces.
The earlier bridges were designed on the free cantilever principle with an expansion joint incorporated at the center. Unfortunately, settlements, deformations, concrete creep and
prestress relaxation tended to produce deflections in each half span, disfiguring the general appearance of the bridge and causing discomfort to drivers. These effects coupled with the difficulties in designing a suitable joint led designers to choose a continuous connection, resulting in a more uniform distribution of the loads and reduced deflection. The natural movements were provided for at the bridge abutments using bearing bearings or in the case of long multi-span bridges, joints at about 500m centers. Special requirements in advanced construction techniques
There are three important areas that the engineering and construction team has to consider: 1) Stress analysis during construction: because the loadings and support conditions of the
bridge are different from the finished bridge, stresses in each construction stage must be calculated to ensure the safety of the structure. For this purpose, realistic construction loads must be used and site personnel must be informed on all the loading limitations. Wind and temperature are usually significant for construction stages.
2) Camber: in order to obtain a bridge with the right elevation, the required camber of the
bridge at each construction stage must be calculated. It is required that due consideration be given to creep and shrinkage of the concrete. This kind of calculation, although cumbersome, has been simplified by the use of computers.
3) Quality control: this is very important for any method of construction, but it is more so
for the complicated construction techniques. Curing of concrete, post-tensioning, joint preparations, etc. are detrimental to a successful structure. The site personnel must be made aware of the minimum concrete strengths required for post-tensioning, form removal, false-work removal, launching and other steps of operations.
Generally speaking, these advanced construction techniques require more engineering work than the conventional falsework type construction, but the saving could be significant.
Bridge rehabilitation
The dividing line between bridge repair or maintenance and bridge rehabilitation is sometimes rather hazy. Often the difference is implied to depend on the extent of repair required to bring the bridge up to an adequate condition. Repair implies fixing a component to a previous condition. Rehabilitation is usually intend to extend the service life of an existing bridge. Several research projects include research on increasing the load-carrying capacity of bridges and rehabilitation of “off-system” bridges.
Rehabilitation may take the form of any one of several restoration procedures. The work can include deck replacement and minor repair or it can involve procedures for correcting settlement problems, strengthening or replacing critical members, replacing bearings, widening or correcting alignments, or improving drainage. Deck replacement
The most common rehabilitation of a bridge is replacement of the deck or the deteriorated portions of the deck. The most common deterioration is the result of chloride ions penetrating the concrete and consequent corrosion of the reinforcing steel. De-icing chemicals placed on the bridge deck are the primary source of chloride ions. The type and extent of deck restoration depends greatly on the chloride content and percentage of deck area contaminated. Often bridge decks with less than 1 lb of chloride per cubic yard at the rebar level are protected by overlaying with a waterproofing membrane or low slump concrete. For bridge decks with greater than 2 lb of chloride per cubic yard of concrete at the
rebar level, commonly called the critical salt concentration, most highway agencies remove the contaminated concrete to below the upper reinforcing steel, sand blast the steel, coat the rebars with an epoxy protection material, and place new concrete.
For bridge decks with extensive chloride contamination, cathodic protection and epoxy grouting are sometimes used. Cathodic protection systems have been used for some time now by a few state agencies on decks with advanced rebar corrosion over significant areas of the bridge deck. Complete replacement of bridge decks is normally recommended if more than 40percent of the surface area of the deck is contaminated. In some cases, temporary patching and pothole repair is used on badly contaminated decks until the corrosion of the rebars or concrete deterioration renders the structure unsafe for legal loads to cross the structure. Normally, the deck replacement incorporates coated rebars in the upper layer and a waterproofing membrane or low slump concrete-surfacing to protect the deck from early chloride contamination.
Girder replacement or strengthening
Several methods are available for repair of concrete bridge girders, depending on the type and extent of repair needed. Some cosmetic patching is used to protect exposed rebars, but as a general rule gluing concrete pieced together has not been successful. Epoxy injection can be successfully used to protect reinforced, particularly prestressed, tendons from moisture. Such application should only be used, however, after the structure has been reanalyzed to take into account any other deficiencies caused by deterioration. This type of rehabilitation may be considered only maintenance, since the structure is restored to a previous condition, and the process slows down the deterioration and may or may not prolong the service life. Other concrete-member rehabilitation includes external steel reinforcement attached to the member by utilizing bolts extending through the member. This external reinforcement can also be post-tensioned if desirable. Supplemental steel or precast concrete members may also be used to increase the overall capacity of a bridge if the floor or deck system is inadequate. Replacement of damaged or critically deteriorated members has been a standard practice by many road agencies. This procedure usually requires careful planning to provide satisfactory results.
Steel members can usually be strengthened by adding cover plates depending on the critical stress mode. Generally, these plates are bolted to prevent stress raisers susceptible to fatigue failure. Steel members usually can be replaced if damage or deterioration renders them ineffective. Replacement of members in a steel tress is common practice. Steel girder bridges may be strengthened also by composite the steel beam. During the replacement of deteriorated decks, studs are welded to the beams to provide the drilling holes through the deck for attaching studs, and epoxy injection between beam and deck. Splicing together simple beams for continuous action is sometimes used to strengthen existing steel bridges. Such strengthening as described requires cognizant engineers for the design of the repair or update.
Dead load reduction
Another method of increasing the load-capacity, which is often easily accomplished, is the reduction of the dead load. In many older bridges, the asphalt overlays have built up until t he dead load from this material is significant. In other situations, the entire deck may be removed and replaced by a lighter weight decking material.
Three materials used for new decks in old bridges are: (1) the open grid steel flooring,(2)
cold formed corrugated metal plates, and (3) laminated timber decking. The open grid has the advantage of letting rain and snow pass through and eliminating the need of a deck drainage system, but the steel may become slippery when wet or ice-covered. The corrugated plate system is placed over existing srtringers and some supplemental lightweight support beams. Here, the drainage system must be adequate to move water or the corrugated metal plate will corrode. The glue laminated or prestressed timber deck is a recent innovation. Prefabricated panels are normally clamped or bolted to existing girders. A properly laminated panel provides adwantages in that it is resistant to chemicals used in snow and ice control. Geometry
Rehabilitation of a bridge may include improvement of the geometry in the form of changing vertical clearances, widening of the structure, or improving the horizontal or vertical alignment.
A common form of bridge damage is vehicular collision resulting from vertical clearance restrictions. This form of damage is particularly common when one or two bridges on a route have significantly less vertical clearance than the other structures. Trusses often fit into this category. Renovation may be accomplished by reducing the depth of portals and sway bracing or by lowering the floor system to increase the vertical clearance. A thinner deck system may also provide some additional clearance.
Overpasses can be raised or the roadway lowered at the grade separations. Both methods have been used by road agencies to improve the vertical clearance.
Numerous methods of roadway widening have been used by the various highway agencies in U.S.A.. The Hackensack river bridge was widened by extending the structure symmetrically about the center line. The John Harris bridge was widened all to one side. The service life of many bridges can be extended appreciably to widening of the structure to meet the minimum standards for today’s traffic. The process is reasonably routine on most bridges and involves removal of sidewalks and curbing, extending piers and abutments, and adding new stringers and a new deck. Mechanical Deficiencies
The bearings, expansions, hangers, and similar devices associated with structural contraction and expansion frequently need rehabilitation. These devices often cease functioning properly as a result of corrosion or debris being built up. Usually, repair involves cleaning these devices and adjusting to the proper position. Minnesota has initiated a program of moving frozen bearings, sand blasting or cleaning the devices, and providing grease inserts so that the bearings may be serviced on a regular basis.
Deck expansion joints frequently contribute to major corrosion problems on bridges by allowing water and chloride solutions to leak through to girders or pie caps. Replacement of joint seals can often improve this situation. Drainage collection systems may be installed, or repaired if already existing, to carry drainage from open joints away from bearings or hangers. Scupper may also be used to control the drainage runoff from the deck. Safety and Serviceability
A bridge may be rehabilitated in several safety areas which include replacement of inadequate bridge railing and alteration of bridge railing or guard railing ends. Alteration of parapets and protection using attenuators at hazardous ends of trusses, piers, or gore areas may accomplish safety rehabilitation of a bridge. Adjusting road alignment can have
substantial impact on the safety record of a bridge.
The serviceability of a roadway can be improved in several ways. Repair of approach slab settlement at the end of bridges can improve the riding quality considerably for many structures. Deck repairs of potholes and slippery areas can also improve the safety and riding comfort of a bridge.
Bridge inspection is now recognized as an essential part of the highway program. If the program is to remain effective, then drainage, deterioration, and other defects must be addressed through a continuing maintenance and rehabilitation program. The huge investment in the highway infrastructure will be erased quickly if proper maintenance and rehabilitation procedures are enforced anedfunded.
From 《English for road and bridge engineering》
2003
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