跨既有高速桥梁大跨径钢箱梁步履式顶推施工关键技术.pdf

85No.32023上海么路SHANGHAHWAYS桥隧工程跨既有高速桥梁大跨径钢箱梁步履式顶推施工关键技术张小欣（安徽省公路桥梁工程有限公司，安徽合肥2 3 0 0 3 1）摘要：针对上跨既有高速公路的钢箱梁施工，由于其交通量大，为保证通行，施工安全的要求高。尤其是大跨径桥梁，拖拉式顶推往往无法满足现场需求。故采用步履式顶推施工是较优选择。就近年来我国自主研发的步履式顶推技术，针对跨既有高速桥梁大跨径钢箱梁施工，简述了其中的施工关键点和难点。关键词：步履式顶推；大跨径钢箱梁；跨既有高速；关键技术0引言随着钢结构技术的发展，跨越能力强、施工快速的钢箱梁在桥梁建设中的应用越来越广泛。顶推法施工立体桥梁，因其不影响桥下既有线形的通行和通航，是一种优秀的施工方法。随着对顶推原理的不断研究，设计理论和施工水平的快速发展，顶推法工艺越来越成熟，已逐渐演变成我国桥梁工程建设中常见的施工方法。大跨径和大截面钢构桥跨越通行高速公路工程，在需保障高速公路正常行车的情况下，对临时支架、顶推施工工艺、施工安全的要求较高。本文以宿松路跨京台高速顶推工程为背景，阐述了步履式顶推法在实际施工过程中的应用。1工程概况及工艺原理1.1工程概况宿松路(卧云路深圳路)6 标段位于合肥市经开区，北起卧云路交口，顺接卧云路以北段宿松路，终于紫石路。包含宿松路主线、方兴大道互通及方兴大道改造段，全长1.7 7 7 km。其中，ES第5联、NE第10联上跨既有京台高速，跨径组合为（4 0+6 0+4 0）m，最大跨径6 0 m。高速主线全宽4 2 m，与线路夹角61，施工离地最大高度15.7 m，施工吨位150 0 t，见下图1。收稿日期：2 0 2 3-0 4-17图1现场施工图1.2工艺原理针对大跨径和大截面钢构桥顶推，顶推施工的最大悬臂长度达到6 0.3 m。顶推期间，高速公路不封路。采用多点步履式顶推系统施工，施工工艺采用3 6 m导梁连续顶推方案，主跨加边跨连续顶推。千斤顶在桥墩上顶推到墩位后，再采用竖向千斤顶，落梁到永久墩。2关键施工技术本文对临时支架施工、导梁施工、智能多点式顶推系统、步履式多点顶推施工等施工关键技术进行介绍。2.1临时支架施工2.1.1拼装支架施工（1)拼装支架采用模块化支架，设置4 组，每组由4根材质为Q235B、（4 2 6 8)mm的钢管柱，通过间距为2.9 m的10#槽钢/角钢联结系，焊接成格构柱，见86上海么路No.32023桥隧工程SHANGHAI HIGHWAYS-下图2。每组钢管柱的长宽尺寸（中到中）为（2.6 51.65)m。(2)每组钢管柱定位后，钢管柱下端头与混凝土条形基础的预埋钢板进行焊接。预埋钢板与钢管柱间设置4 个加劲肋，加劲肋尺寸为（150 7 510)mm。钢管柱上端头焊接封板，封板采用12 mm厚度的钢板，封板尺寸为(6 0 0 6 0 0)mm，见下图3 和图4。(3)双拼3 2 a#工字钢满焊，焊接成一体。中间腹2650-1650-产钢垫块支点双拼3 2 a#工字钢10#槽钢/角钢426*8钢管10#槽钢/角钢混凝土基础或预制钢基础3003650-2650混凝土基础650或预制钢基础426-10加劲板预埋钢板50265075500-426*8钢管250钢条锚固筋36501图2 拼装支架大样图（单位：mm）7.70015004700500分山山山田广Wmmmmm mmmmm3366006*5002.6503.650图3 拼装支架立面图（单位：mm）图4 拼装支架现场图872023No.3上海么路SHANGHAIHIGHWAYS桥隧工程板位置，每隔1m设置1个加劲肋补强，加工后作为横向分配梁。分配梁落在钢管柱的上封板上，在工字钢分配梁的两侧，焊接限位码板，防止工字钢位移。测量放样后，在工字钢分配梁上，焊接钢垫块临时支点。钢垫块采用2 5a工字钢焊接而成。(4)拼装支架承受最大荷载(2 6 7 8)kN，经计算，拼装支架受力和稳定性均满足要求，见下表1。表1拼装支架计算结果表（单位：MPa）结构 426 mm钢管柱柱顶分配梁联结系组合应力977818剪应力16812.1.2顶推支架施工(1)顶推支架结构分两类：一是非主墩处纵移支架，二是纵移分配梁穿越主墩。顶推位置设置4 组，每组由4 6 根截面为（6 30 10)m m 的钢管柱及14#槽钢联结系组成格构柱，钢管柱间距3.0 m3.0m。柱顶和千斤顶分配梁均采用双拼（7 0 0 30 0 2 4 14)mm的H型钢,联结系为 14 槽钢(非主墩)或(2766)mm钢管（主墩），见下图5。(2)经计算，顶推支架受力和稳定性均满足施工要求,见下表2、表3。2.2导梁施工导梁是多点步履式连续顶推施工中必不可少的结纵移支架立面图1700215316972153mmmn广5002.9002.900829002900505003.00030003000图5J顶推支架立面图（单位：mm）表2非主墩处纵移支架计算结果表（单位：MPa）结构630mm钢管柱柱顶分配梁千斤顶分配梁联结系组合应力13728103124剪应力572712表3主墩处纵移支架计算结果表（单位：MPa）结构630 mm钢管柱柱顶分配梁千斤顶分配梁联结系组合应力841759100剪应力6279852023No.388上语么路桥隧工程SHANGHAI HIGHWAYS-构，能起到减小主梁顶推长度、引导主梁顶推搭设、纠偏主梁方向的重要作用 2 。顶推梁段前端设置36 m长变截面导梁，导梁结构由2 片实腹式不等截面工字形钢板梁组成。工字钢截面(2 8 0 0 1 50 0)mm600mm18mm20mm,两片导梁每隔8 m设置一道横向联系，由上、下弦杆(3518)mm钢管及斜杆(2766)mm钢管组成。另外，为保证导梁工字钢腹板的局部稳定性，沿纵向及横向均设置了加劲肋板。导梁根部截面的上、下翼缘板及腹板与钢箱梁的顶、底板及内腹板厚度均相同，方便焊接，并保障了导梁与钢箱梁的可靠连接，见下图6、图7。立面图067X:50-395002802X5001/21-12003000001/2.22图6 36 m导梁设计图（单位：mm）3-310501.65010506002100600315200202003153152002020031590200202009090200202009022556-66002100600902002020090902002020990600210060090200.20209J99090L200.2020990G4911S908图7 36 m导梁横断面设计图（单位：mm）89No.32023上涵么路SHANGHAITXA桥隧工程2.3智能多点步履式顶推系统钢梁顶推采用智能三维千斤顶调整系统。根据顶推用临时支墩数量，安装垂直2 50 t、纵向50 t的高压液压三维千斤顶。顶推设备负责钢梁的竖向起顶、纵向推移，同时自带有顶推施工时的横向限位功能。步履式滚动摩擦水平顶推系统由滚动摩擦步履器、液压泵站及PLC变频同步液压控制系统组成。多点步履式自平衡顶推体系施工关键技术为多点顶推和压力调节。可采用计算机控制同步顶推，避免桥墩受到集中荷载；计算机控制液压同步下降，避免单个顶升油缸受到偏载。2.3.1液压泵站及PLC变频同步液压控制系统本系统的工控界面软件采用组态软件，主控系统的执行系统采用PLC可编程控制器。位移检测装置和压力传感器的信号由信号电缆连接到液压系统的电气控制箱内，经信号放大器放大后，将顶升位移和负荷吨位送至可编程控制器PLC中。可编程控制器PLC根据触摸屏发来的操作指令，启动电机驱动油泵，工作油泵的动力油源经控制阀组，输出到外接的液压油缸中，使液压油缸上下运动。同时，可编程控制器根据检测的位移信号，不断与指令信号进行比较，修正误差值后，改变继电器的输出频率，以改变电机的转速变流量，最终满足液压油缸同步上下运动，实现油缸运动速度可调。每台泵站控制2 台滚动摩擦步履器。泵站有2 个方向阀组，分别控制滚动摩擦步履器的三个方向；1个限压阀组，可切换高低压使用。2.3.2滚动摩擦型步履式顶推及纠偏装置本次顶推施工步履器采用专利产品滚动摩擦型步履器。该产品摩擦因数小于0.0 6，有效解决了桥梁在顶推过程中产生的震颤现象。滚动摩擦型步履式顶推装置由垂直千斤顶、横向纠偏顶、纵向顶推顶、重物搬运器、底座等组成，见下图8。底座采用钢结构作为支撑底座，结构紧凑，能够有效支撑垂直顶的顶推。垂直顶底部安装的MGB板构成滑移接触面，其摩擦因数小于0.1,保证了垂直顶在桥梁顶升过程中，横向纠偏的微小位移滑动。根据监测数据，调整纠偏千斤顶，使钢梁在预设的桥梁线路中顶推。下部重物搬运器的摩擦因数小于0.0 6，保证了纵向顶推顶在桥梁顶推过程中的顺滑移动。垂直顶升千斤顶采用2 50 t千斤顶，直径（350 38 0)m m，行程2 0 0 mm。顶推千斤顶采用50 t纠偏油缸顶升油缸顶推油缸重物移运器图8 滚动摩擦型步履式顶推装置示意图千斤顶，行程50 0 mm。纠偏千斤顶采用50 t千斤顶，行程150 mm。本工程由于钢箱梁底部为拱型且不一定平整，为保证千斤顶负荷一致，在垂直千斤顶上部装有抗偏载鞍座。设备工作特点如下：垂直顶升油缸接触负载低压找平后，开始带负载上升，至预定高度时，垂直顶升油缸由液压锁保持住位置不变。纵向顶推油缸带动负载，推进至指定纵向位置。若发现梁体横向与预定位置偏离超过设定值，则需要在竖直顶升油缸顶起梁体时，对梁体进行纠偏。三向千斤顶的拉线式位移传感器，能实时监控三向千斤顶的垂直顶、横向纠偏顶、纵向纠偏顶的位置和位移情况。利用“顶”和 推”两个步骤交替进行，先将整体钢箱桥面托起，再向前推送，之2023No.390上涵么路（桥隧工程SHANGHAI HIGHWAYS-后将钢梁置于桥墩上，顶推油缸缩缸到底，继续实现下一个循环。通过往复顶推步骤的循环，最终，箱梁被送到预定的位置。设备优点如下：承载能力大，可调整大吨位的重载构件或设备，并可根据实际工程需要，调整承载能力。调整精度高，三维控制X/YIZ三个方向，均可达到1mm的精确调整和定位精度。系统操作方便，操作工人经过简单培训，即可熟练掌握操作，并实现预期调整精度控制。与滑动摩擦型步履器相比，摩擦因数小，纵向顶推力更小。由于摩擦全部是在顶推装置内部进行的，桥墩不受水平荷载。顶推装置分布在各桥墩上，形成多点推进，保证了箱梁的前进方向。即便有少量偏斜，通过两侧支撑油缸也可以做灵活的纠偏工作。横向调整油缸保证钢箱梁水平移动，不会产生偏移。整套设备集顶升、平移、横向调节于一体，成本低，见下图9。SHOTONMAIDUALCAMERA图9 顶推设备大样图及现场安装图2.4步履式多点顶推施工2.4.1顶推装置工作原理顶推装置的工作原理见下图10，顶推步骤见下图11 14。步骤一（顶升）：开启支撑顶升油缸，使得支撑顶升油缸同步上升，直到钢梁脱离落梁调节支座。步骤二（平推）：开启顶推油缸，使钢梁与上部滑移结构整体前移，直至平推油缸完成一个行程。步骤三（下降）：开启顶升油缸，使得钢梁与上部滑移结构整体下降，直到顶升油缸完全脱离钢梁。步骤四（回缩）：开启顶推油缸，使上部滑移结构向后回位，回到初始位置，并开始下一个往复行程。托染顶升千斤顶纠偏干斤顶顶推千斤顶搁墩重物移运器图10 顶推装置工作原理图2023No.391上海么路SHANGHAI HIGHWAYS桥隧工程）钢梁垫梁垫块顶步履式千斤顶设备平创图11步骤一(顶升）钢梁垫块步履式千斤顶设备平创图13步骤三（下降）2.4.2顶推施工步骤顶推施工共分9 个节段进行施工。节段最长2 2 m，仅安装段设置临时支架，分列如下。工况一：导梁及相邻5节段箱梁拼装完成，起顶状态。工况二：剩余2 节段箱梁拼装完成，起顶状态。工况三：钢梁脱离纵移支架Z1,纵移支架Z2、Z 3、Z4受力，尾部悬臂2 9.5m，前端悬臂51.5m。工况四：导梁前端上墩前，前端悬臂6 0.3m，钢梁部悬臂2 0.7 m。工况五：钢梁尾部与纵移支架Z2脱空。此时，前端悬臂2 1.1m，尾部悬臂2 7.5m。工况六：导梁及钢梁至设计里程位置。此时，前端悬臂4 0.8 m，尾部悬臂7.7 m。工况七：拼装剩余梁段并落梁。2.4.3钢箱梁结构、抗倾覆及稳定性验算采用Midas对钢箱梁建模，梁单元模拟。经过计算，顶推最大反力2 16 6 kN，配置30 0 t步履千斤顶，满足要求。顶推强度导梁在工况五下的最大组合应力和钢梁垫染垫块平推图步履式千斤顶设备平台图12步骤二（平推）钢粱垫块垫梁回缩步履式千斤顶设备平创图14 步骤四（回缩）剪应力为8 1MPa和16 MPa，箱梁强度在工况四下的最大组合应力和剪应力为12 7 MPa和2 0 MPa。顶推刚度在工况四下的导梁最大扰度56 8 mm，纵移高程预抬150mm。满足上墩要求。工况四支撑状态下（支承点分别位于纵移支架Z2、Z 4、Z 3脱空时）的向前抗倾覆系数最小。根据受力状态，计算向前抗倾覆安全系数为4.8 5。按照公路桥涵施工技术规范（JTG/T3650-2020)17.8.11的规定，钢箱梁安装作业时，抗倾覆稳定系数应不小于1.3，故满足要求。工况三支撑状态下（支承点分别位于纵移支架Z2、Z 4、Z 3脱空时）的向后抗倾覆系数最小。根据受力状态，计算向后抗倾覆，安全系数9.2 8 1.3，满足规范要求。钢箱梁顶推过程中，支点处的最大反力为（2 2166)kN支点截面处的最大轴弯矩My=44801kNm，剪力V=2186kN。箱梁高2 8 0 0 mm，腹板厚度14 mm，每1.5m布置一道横隔板。对钢箱梁该位置的腹板局部稳定性和导梁稳定性进行计算，均满足规范要求。2023No.392上语么缘上接第7 3页）桥隧工程SHANGHAI HIGHWAY顶推施工时，墩身受力按最不利荷载下考虑，底部主拉应力分布在0.9 1.1MPa之间，小于容许值2.4 3MPa，满足规范要求2.4.4钢梁线形控制措施顶推作业时，要求每安装一个节段，各节段测一次挠度，与计算值比较；同时测一次中线，判断钢梁的制造和安装质量，并决定纵向坡度，使钢梁在到达前方支点时，梁底与墩顶之间有足够的净高度，以便布置起顶设备。下一步，应考虑是否采用纠偏装置横移钢梁。此外，还应观察测量各墩支点位移情况，以便与设计值比较。同时，对关键分块也需进行应力测定，并与计算值比较，及时分析，防止超应力。3结语对于需保障高速公路正常行车的大跨度桥梁施可能性较低，因此，高密度人群下，略低的行人舒适度等级是可接受的。梁高1.0 m的方案，所需的阻尼器设备较多，工程成本上升，并由于存在与主梁侧向相连的电梯和梯道等设施，对主梁侧向振动具有一定的阻碍作用，能够有效降低主梁侧向振动响应，改善行人舒适度。因此，该人行桥采用了梁高1.15m方案，并采取文中的MTMD布设方案作为最终设计。5结语本文以某三跨钢箱连续梁人行桥为背景，针对高密度人群通行下的人致振动舒适性问题，结合三种梁高方案，进行了分析评价，并结合TMD措施，进行了减振控制。主要结论如下：(1)采用德国EN03规范的行人激励分别对1.4 m、1.15m、1.0 m 三种梁高方案进行加载。分析结果表明，随着梁高的降低，对应模态振型的振动响应程度增加。据此，本文以ENO3规范为基准，选出舒适度评级最低的结果，作为主要控制振型。(2)通过在主要控制振型的相关控制点位处布设对应控制方向的TMD，形成全桥MTMD系统，进行减振控制。结果表明，在相同的行人激励加载下，对应模态振型的振动响应显著减小，舒适度评级提升至CL1工，合理设置临时支架，是其安全施工的关键。对导梁进行优化，选用合理的导梁尺寸，能够节约材料，提升安全系数。而针对桥梁顶推过程中产生的震颤现象，本顶推系统采用专利产品一一滚动式摩擦步履器，有效解决了该问题。钢梁顶推施工过程中，保证成桥线形也是一项难点，可采取线形控制的措施。本文结合桥梁自身特点和施工工艺，对钢箱梁步履式顶推施工关键技术进行了介绍，具有较好的参考价值。参考文献1石志祥,石初国,刘承飞,等.城市高架大跨度钢箱梁步履式顶推施工技术 C/施工技术(中英文)杂志社,亚太建设科技信息研究院有限公司.2 0 2 2 年全国工程建设行业施工技术交流会论文集（下册）.出版者不详,2 0 2 2:37-4 1.2贾红兵.钢箱梁步履式顶推法施工关键技术研究 D.西安：长安大学,2 0 19.级（最好）。由此说明，在满足结构极限状态设计要求的情况下，以舒适性作为控制目标，进行减振设计，可以对梁高进行合理选择，以实现行人舒适性和结构经济性之间的平衡。参考文献1陈杰,艾辉林,王声云.基于TMD的连续多跨曲线人行桥减振设计研究 J.中外公路,2 0 2 2,4 2(0 5):7 2-7 7.2华旭刚,温青,陈政清，等.大跨度双层曲线斜拉桥人致振动减振优化与实测验证 J.振动工程学报,2 0 16,2 9(0 5):8 2 2-8 30.3李爱群,陈鑫,张志强.大跨楼盖结构减振设计与分析 J.建筑结构学报,2 0 10,31(0 6):16 0-17 0.4王均刚,马汝建,赵东,等.TMD振动控制结构的发展及应用J.济南大学学报(自然科学版),2 0 0 6(0 2):17 2-17 5.5周望,周彦锋,马如进.大跨径人行桥人致振动舒适性研究J.城市道桥与防洪,2 0 2 0(10):7 3-7 6+14.6操礼林,钱程,张志强,等.人行荷载模型与人致结构振动试验研究 J.东南大学学报(自然科学版),2 0 18,4 8(0 1):113-117.7尚旭强.基于双足模型的人-桥竖向动力相互作用研究 D.兰州：兰州理工大学,2 0 2 1.【8 】中华人民共和国建设部.城市人行天桥与人行地道技术规范：CJJ69-95S.北京：中国建筑工业出版社,19 9 6.9 Schlaich M.Guidelines for the design of footbridges M.Guidelines for the design of footbridges,2005.Analysis of the Force and Influencing Factors of Large-span PC Beam FloorAbstract:The large-span PC beam with box section is the most widely used and most common scheme of medium and large span girderbridge.In the long-term operation process,typical representative diseases such as beam cracking and mid-span deflection have also beenfound.Bottom plate cracking is a more common type of disease.In this paper,the influence of constant load and live load on the force of thebase plate is revealed through the quantitative calculation of different influencing factors,and a structural optimization design scheme is pro-posed on this basis.Key words:large span PC beam;box-type section;bottom plate cracking;transverse frame calculation;bottom plate bundle collapse forceDiscussion on the Influence of Gradient Temperature and other Effect on the Anti Overturning Calculation ofSteel BoxGirdersAbstract:Municipal bridges mostly use single-column vase piers,which have a beautiful shape and save road space.However,due to thesmall spacing between its supports,overloading and other factors,multiple beam overturning accidents have also occurred in recent years.This article provides a detailed discussion on the anti overturning calculation of bridges based on current specifications and practical engineer-ing,aiming to provide reference and reference for future bridge design.Key words:steel box girder;anti overturning;specificationDesign Practice and Summary of Low Clearance River-crossing Bridge Slow Passage through ReconstructionAbstract:Taking waterfront space as the starting point,creating a charming quality urban area with temperature,vitality and characteristics,realizing the connection of waterfront and returning the shore to the people will become an important means of urban renewal in the future.Among them,the small bridges of municipal roads across non-navigable rivers often become the breakpoints of riverside slow-moving walk-ways because of the low clearance under the beams.Combined with the practice of similar projects in recent years,this paper sums up the re-construction methods for the slow passage under the low clearance river-crossing bridge,and points out the progressive reconstruction strategywith three types and seven grades,so as to provide some reference for similar projects in the future.Key words:low clearance;under the bridge across the river;slow move channel;through recongstructionComfort Analysis and Vibration Reduction Control of Pedestrian Bridge with Three Span Steel Box Continuous Beam underHuman Induced VibrationAbstract:With the increase of footbridge span and the wide application of lightweight and high-strength materials,the fundamental frequen-cy of the structure is constantly decreasing,which brings a significant problem of comfort of human-induced vibration on bridges.Based on hu-man-induced vibration theory,this paper analyzes the action characteristics of pedestrian load and the similarities and differences between do-mestic and foreign standard evaluation methods for pedestrian comfort.Finite element simulation calculation is used to analyze the human-in-duced vibration response under high-density crowd,and three different beam height schemes are compared,together with their human-in-duced vibration effects and the effects of applying vibration reduction measures.The results show that the vibration control measures based onmultiple TMD have good cost control feasibility under the premise of ensuring the human-induced vibration performance of steel box girderfootbridge structure.Key words:pedestrian bridge;human-induced vibration;damping control;TMDApplication of Jacking and Sliding Technology of Steel Structure Bridge in Chunshentang Bridge Project onJinghong RoadAbstract:With the rapid development of infrastructure construction in China,steel structure bridges have been widely used.Steel structurebridge installation usually uses installation techniques such as large lifting machinery and bridge erecting machines.However,due to limita-tions in the construction site and environmental factors,some projects cannot adopt conventional methods for the installation of steel structurebridges.In recent years,the push sliding technology has gradually been widely applied in the installation of steel structure bridges.Taking thenew construction project of Chunshentang Bridge on Jinghong Road(Jindu Road-Huajing Port)as an example,this article aims to provide ref-erence for similar projects.Key words:steel structure bridge;top push;slippageResearch on the Force of the Transverse Beam of Wide Multicell Concrete Box GirderAbstract:The force of the transverse beam for wide concrete box girder is relatively complex,and the force transmission ratio between the topand bottom plate and the web plate in the simplified calculation of the beam in the conventional design may have a large deviation from the ac-tual force.In order to get the real force mode of the beam,the three-dimensional solid finite element analysis is used to accurately calculatethe force transfer ratio of the top and bottom plates and the web plates.The reasonable prestress layout of the beam is obtained through the cal-culation of Dr.Bridge 4.4.Key words:bridge engineer finite element;beam calculation;wide;force transmission ratio;prestressing forceKey Techniques for Walking Type Jacking Construction of Large-span Steel Box Girders for Bridges AcrossExisting HighwaysAbstract:For the construction of steel box girders crossing existing highways,due to high traffic volume,high safety requirements are re-ZHANGYan(52).CHENNan(56)HUANG Chenghua(60)HEWei,LU Haixiao,ZHU Jianfeng(68)XURen(74).GUAN Ruyi,JIANG Kai,XU Changze,ZHAO Hongjiao（8 1)ZHANG Xiaoxin(85)LULingxia（9 3)quired to ensure passage.Especially for large-span bridges,the drag jacking is often unable to meet the site requirements.Therefore,the useof walking jacking construction is the preferred choice.This article briefly describes the key points and difficulties in the construction oflarge-span steel box girders spanning existing high-speed bridges using the walk-type pushing technology independently developed in Chinain recent years.Key words:walking push;large span steel box girder;crossing existing highways;key technologyDiscussion on the Construction Scheme of Steel Boxed Cofferdam with Bottom for High Pile Cap in Deep WaterAbstract:Based on the Boluo-Dongjiang Bridge reconstruction and expansion project of provincial highway-S255 as the background,this pa-per introduced the construction process of a steel boxed coferdam with bottom for high pile cap in deep-water environment.The bottom plateand bottom beam of the casing are made of precast reinforced concrete.When the first stage of concrete pouring is complete,weld the bearingbracket on the pile steel casing,for the sake of convert the stress of the main structure of the cushion cap from the suspension system to thebearing bracket.The control points of the casing structure construction process are introduced in detail,which provides reference for similarpile construction.Key words:high pile cap in deep-water;steel boxed cofferdam;prefabricated bottom beam and base plate;transformation of stressed sys-tem;bearing corbelConstruction Technology of Four Line Cast-in-place Beams Abstract:The Tianhai section is located in the SG7 section of the first phase civil engineering project of the S2 line of the Wenzhou city rail-way,which is in the southeast coast with heavy rainfall