本科桥梁专业毕业设计.doc

本科桥梁专业毕业设计长安大学 毕业设计（论文）任务书一 设计内容（论文阐述的问题）1 拟定桥型比较方案三个。2 择优推荐方案。3 进行推荐方案上部结构内力分析，截面设计。4 进行推荐方案的施工验算。二 设计原始资料（实验、研究方案）1 桥位地址剖面图2 桥面设计标高434.713 平曲线半径R=4 纵坡i=05 单向横坡i=2%三 主要技术指标1 设计荷载：汽超20级。2 桥面净宽：0.5+11.25+2.0+11.25+0.53 桥位气温：平均最底-12.3，最高+38.14 地震烈度：7度四 设计完成后提交的文件和图表（论文完成后提交的文件）1 计算说明书部分：1） 设计指导思想、重点、难点2） 各个方案的特点，推荐方案的被选理由3） 推荐方案上部结构的结构计算书、截面设计计算书4） 推荐方案施工验算书5） 施工中注意事项6） 设计小结2 图纸部分：1） 方案比较图2） 推荐方案整体布置图3） 推荐方案施工示意图4） 推荐方案上部结构配筋构造图5） 细部构造图五 主要参考资料1.公路工程技术标准JTGB01-20032桥规3教材：桥梁工程、结构设计原理、基础工程、桥梁电算4与推荐方案相类似的手算实例。The Design of Luo-Xi Bridge,GuangdongGeneralThe Luo-Xi bridge,Guangdong,now under construction is a four lane highway bridge downstream of Zhu-Jiang River.The main bridge is designed jointly by Highway Planning and Design Institute,MOC and Highway Surveying,Planning and Design Institute,Guangdong.The whole bridge is constructed by Construction Division,Department of Communication,Guangdong Province.This bridge is at south part of Guangzhou city,across the Zhu-Jiang River.The width of the river is 461m,average depth of water 7.28m,average velocity of water 0.97m/sec.The bed is covered with sand of medium size,clay and weathered sandstone etc.,average thickness 19.2m.The bedrock is brown sandstone which has an average compressive strength 10MPa.The flow is steady and scouring of river bed is not great.Shipping boats are 50007000t,navigation width 120m,height 34m.Because the navigation is not closed at construction period,any construction equipment enter the navigation channel is not permitted.Three alternatives were considered in selecting the type of bridge.These are:continuous rigid frame bridge with main span of 180m,continuous grider bridge with mian span of 150m and cable stayed bridge with 2 pylons with mian span of 230m.As the persent trend is to eliminate expansion joints as well as bearings in the design of long bridges,after technical and economical comparison,the scheme of 65+125+180+110m continuous rigid frame is finally adopted in the design.The main bridge is 480m long with expansion joints provided only at its junctions with approaches,and the super-structure of the mian structure is completely integral with the piers to form a rigid frame.Single box is used for superstructure of main bridge.Height of box is 4m at bearing of No.2 pier,and 10m at bearing of No.3 and No.4 pier,and 3m at the closure section of the spans.Each of the two main piers in the river supporting the superstructure is composed of two reinforced concrete legs with dimension 2.28.0m,placed on pile cap immersed in water.The pier is supported by a group of 1.5m cast in situ reinforced concrete bored piles.No.2 pier rests on 12 bored piles each 24.2m long,and No.2、No.4 piers rest on 24 piles with average length of 47.3 and 27.1m respectively.To prevent damage of main pier due to ship collision double wall circular steel cofferdam with diameter of 28m at top and 23m at bottom are used around No.3 and No.4 pier serving as encircling structure of artificial island.Pot rubber bearings which allow only longitudinal displacement are provided at the end piers of main bridges to transmit lateral shear force.The general layout of whole bridge is shown in fig.1.ConcreteConcrete with 28 days strength of 50MPa is used for superstructure and No.2、No.3、No.4 pier walls,and concrete with strength of 30MPa is used for No.1、No.5 pier walls and pile caps,and concrete with strength of 25MPa is used for piles.Different test mixes of concrete are required to find the suitable consistency to facilitate the casting of concrete at deep bottom parts of box section in which the reinforced steel and prestressed tendon are densely distributed. Durability, appearance and watertightness of concrete shall conform to the appropriate requirements, and the requirement to remove the form one day after casting of concrete and to take load after three days of casting shall also be observed.Comprehensive tests shall be undertaken before construction to ascertain the modulus of elasticity as well as creep and shrinkage characteristic of concrete.Post tensioned tendon and prestressing systemPost tensioned tendon of superstructure is composed of wire strands and high strength bars.Table 1 gives the characteristic of the pretressed steel.The seven wire strand is supplied by VSL HongKong,and high strength bars domestic product.Table 1. Characteristies of Prestressing SteelItemsSeven wire strandsHigh strength barsNominal diameter (mm)12.832Nominal cross section(mm2)99804Ultimate strength(N/mm2)18651028Yield strength(N/mm2)1665765Relaxation(1000/h,20,initial stress is 0.7 ultimate strength)7%5%All the longitudinal pretressing tendons are 1912.8mm or 3112.8mm strands,anchored at one end by EC5-19 or EC5-31 VSL anchor respectively,which has ultimate tensile strength 3496kN and 5704kN respectively,and the tensile force adopted is 75% of ultimate tensile force.Frictional loss is rather small due to relative straightness of duct,hence the strands having length less than 70m are prestressed only at one end,and prestressed at both ends for longer length.The longest continuous tendon of main span exceeds 190m,which is the longest prestressed tendons used in our country.EC5-31 VSL anchor is used for transverse prestresssing, prestressed alternatively at distance center to center 100cm.Single or double32 finish rolled,deformed high strength bars ,spaced at 50cm cc.are used as vertical prestressed tendons of webs.Three way of prestress is used in this bridge,The domestic32 finish rolled,deformed high strength bars are used as vertical prestresssing bars,and VSL prestressing systems are used as longitudinal and transverse prestresssing strands.Six kinds of strands are used,which are strand at top slab,strand at bottom slab ,draped strand ,continuous strand ,post strengthening strand ,and temporary strand .Table 2 shows kinds and quantities of strands used at different locations.Table 2. Types、Kinds and Quantities of Strands at Different LocationsItems65m mid spanTop of No.2 pier125m mid spanTop of No.3、No.4 pier180m mid span110m mid spanStrand at top slab (EC5-31)2262Draped strand(EC5-31)88Continuous Strand (EC5-31)444444Strand at bottom slab (EC5-19)26304026Post streng thening strand(EC5-19)4444Temporary strand (EC5-19)2222The type of strand at top slab is determined by dividing the total required prestressing force at the end section by the effective prestresssing force of each strand and total number of segments and shall be 24.Strands bent vertically as well horizontally ,i.e.bent in space ,are used for longitudinal strands.Strands in top slabs have its anchorage concentrated at the haunches at top of web ,strands in bottom slabs shall be anchored as close to webs as possible.This will reduce local stress and at the same time transmit ,in a short path ,the concentrated prestressing force to the whole cross section.The complicated anchorage splays may be avoided by anchoring the top slab strands in the haunches.When the longitudinal strands at top and bottom slabs are shifted horizontal plane in order to anchor at given location ,it shall be shifted in a S curve to eliminate the lateral component of force induced at anchorage by the concentrated prestressing force .Allowance is provided for the deviation due to longitudinal vertical curve of deck ,and this is considered in the coordinates of strand ducts.Type and main dimension of section of superstructureAs the moment at pier section of superstructure due to dead load constitutes 84% of the total moment and the moment at closure section is only 5% of the total moment at pier section ,the main concept of selecting types and main dimension of section is to reduce dead weight and to increase the effective resisting capacity of cross sections ,The measures are:a. To reduce self weight and extra top and bottom slab area to accommodate great unmber of tendons ,large capacity VSL prestressing system is first introduced with jacking 4275kN.With the use of large capacity prestressing system ,the dimension of top and bottom slab are entirely governed by the loading requirement ,thus resulting in more than 60% saving in top and bottom slab sections compared with the 24 wire .Freyssinet system now in use. Besides the notable saving in cost ,it facilitates design and construction work ,and shortens the construction period.b. Use single box section with thin walls to increase moment of inertia per unit area. c. The height of closure section is selected as L/60 to reduces the dead weight but provides sufficient rigidity.d. The torsional rigidity of closed single box section is 60 times that of open section. The ratio of span to width is 11.6 .After accurate analysis ,it is found that torsion has only a little effect on internal force. Hence no diaphragm is used except at pier section ,this reduces dead weight and facilitates construction. Type of main pier Twin flexible legs of thin hollow box section are used as pier to provide greater longitudinal flexural rigidity and torsional rigidity in plane so as to accommodate for longitudinal moment produced by unbalanced construction loads as well as torsion in plane produced by lateral wind load during the cantilever construction of bridge. This type, twin flexible legs of thin hollow box section, uses 40% less concrete than solid section and has greater flexural rigidity and torsional rigidity than single column pier of the same cross sectional area, and ,in addition ,has less thrust resisting rigidity so that the internal forces due to temperature, creep and shrinkage are reduced.Type of foundationDue to the presence of a rather thick clay layer at No.3 pier of main bridge, bored piles have to be used, its diameter 1.5m,so determined by the equipment as well as experience of the constructing party.Structure of artificial islandThe designers paid good attention to the ship collision which had caused many serious damages. As is well known, the effective preventive measure is to construct artificial protective island around pier. After studying comprehensively the scouring of river bed, depth of water, the thickness and types of overlying soil, and the depth of rock layer, the designer concluded that it is feasible to use artificial island in this bridge, the reasons are:a. Height of double wall steel cofferdam, acting as encircling structure of artificial island, is only about 20m after taking account of navigation water level and scouring depth.b. The 19.25m high double wall steel cofferdam at No.4 pier can embed directly on rock layer which underlies at shallow depth, and the overlying layer above rock is medium and fine sand through which the cofferdam sinks without much difficulty. The rock layer at No.3 pier underlies at greater depth, but there is a layer of clay on top of rock and the cofferdam may rest at the desired depth in this layer. On top of clay layer there is also a layer medium and fine sand.Economical indexesPart of the economical indexes of this bridge is given in table 3.Table 3. Indexes per Square MeterItemsConcrete(m3)Strand(kg)Ordinary reinforcement(kg)Box girder of superstructure1.0966.5166.5Main piers No.2No.40.2136.17Side piers and foundation1.7171.73Total3.0166.5274.22Construction methodsThe double wall cofferdam is sunk to the design elevation by sand blowing and then is refilled to form the artificial island. The works about pile construction then proceed on the artificial island. No.2 pier is constructed by lifting from method while No.3 and No.4 piers are construcated by slip form method. The zero blocks(segment over pier support)are cast on falsework and brackets respectively. Two pairs of traveling carriages are used, enabling simultaneous carrying out by cast in place balanced cantilever segmental construction method on No.3 and No.4 piers. Design weight of each traveling carriages is 1088kN,maximum weight of load carried is 1784kN.There are 24 pairs of balanced cantilever casting work for each main T of No.3 and No.4 piers, ten working days of skilled labour are required for each operating cycle of 2 segments. The 20m and 30m length cast in place portions of the side span are poured on falsework.广东洛溪桥主桥设计总体设计广东落溪大桥是跨越珠江下游主航道的一座四车道公路桥。主桥由交通部公路规划设计院与广东省公路勘察规划设计院共同设计，广东省公路工程处施工。该桥位于广州市南郊，横跨珠江，江面宽461m，平均水深7.28m，平均流速0.97m/s。河床表面被中砂、淤泥和风化岩等所覆盖，平均厚度为19.2m。基岩为红褐色泥质砂岩，平均抗压强度10MPa左右。河床冲刷不大。通航海轮5000吨级7000吨级。净跨120m，通航净高34m。由于在施工期间通航不能封闭，所以不允许任何施工设备进入通航河道。有三种桥型方案可供选择。这三种桥型方案是：主跨为180m的连续刚构；主跨为150m的连续刚构和主跨为230m的门式斜拉桥。根据当前国际长大桥向着无支座、无伸缩缝发展的趋势，以及从技术经济上进行比较，选定主桥结构为65+125+180+110m的连续刚构作为最终的设计方案。主桥全长480m，除两端与引桥连接处设置了伸缩缝外，在主桥全长范围内，上部结构与墩身的连接全部采用了整体结构。主桥上部采用单箱单室，2号墩顶处梁高4m、3号和4号墩顶处梁高10m，在各跨合龙处梁高3m。主墩采用截面尺寸为2.28.0m钢筋混凝土空心双柱墩。桩基用1.5m直径的嵌岩桩，两个主墩分别由桩长47.3m和27.1m的24根桩组成。为了避免主墩因船舶撞击而造成损坏，在主墩外围设置了上部直径为28m、下部直径为23m的双层钢围堰作为人工防撞结构。在主桥两端的边墩上设置了只允许纵向位移的盆式橡胶支座。主桥的总体布置见图1。混凝土上部结构及2、3、4号墩墩身采用28天强度为50MPa的混凝土，1、5号墩墩身及各墩承台采用30MPa，桩基采用25MPa混凝土。设计要求进行不同配合比的混凝土试验，以便找出最佳配合比。同时要求有足够的和易性，以便浇注到钢筋和钢束密布且很深的箱梁底部去。此外耐久性、外观、水密性均应满足常规要求，也应保证一天以后拆模和三天加载的标准。为了确定弹性模量和了解混凝土的收缩徐变特性，要求在施工前进行综合性的实验。后张预应力体系上部结构采用由钢绞线和粗钢筋组成的后张预应力体系，表1给出了预应力钢材的特性。7丝一根的钢绞线由香港VSL公司提供，粗钢筋为国内产品。表1 预应力钢材特性项目七丝钢绞线粗钢筋标准直径(mm)12.832标准截面积(mm2)99804极限强度(N/mm2)18651028屈限强度(N/mm2)1665765100h,20松弛率(初始应力为极限应力的75%)7%=12mm II级螺纹钢筋，直径=12mm 级光圆钢筋；锚具：XM锚或 OVM锚主要参考资料：1:土木工程专业毕业设计指南桥梁工程分册2:桥梁工程 教材3:结构设计原理 教材4:基础工程 教材 5: 桥涵水文 教材6:桥梁计算示例集 人民交通出版社出版7:桥梁上部结构计算示例(二) 重庆交通学院等校合编主要技术指标:JTJ 021-89公路桥涵设计通用规范 JTJ 022-85公路砖石及混凝土桥涵设计规范 JTJ 023-85公路钢筋混凝土及预应力混凝土桥涵设计规范 JTJ 024-85公路桥涵地基与基础设计规范 方案比选序号方案类别 比较项目第一方案第二方案第三方案主桥：预应力混凝土连续刚构桥(75m+136m+75m) 预应力混凝土连续梁（三跨）（80m+130m+80m） 预应力混凝土连续梁桥（四跨）(55m+2x90m+55m)1桥高（m）434.71434.71434.712桥长 (m)2862902903工艺技术要求采用悬臂施工法在桥梁设计中要考虑施工过程中的受力状态及由于体系转换和其他因素引起的附加内力.技术先进，工艺要求较严格.但采用悬臂施工体系转换较多，施工线形及合龙技术要求较高.需大吨位支座.技术先进，工艺要求较严格.但采用悬臂施工体系转换较多，施工线形及合龙技术要求较高.需大吨位支座.4施工难易程度桥梁上部采用挂篮悬臂浇注施工，施工时要对称浇注，应注意立摸高程的合理设置，准确控制悬浇高程，施工要求较高.采用挂篮悬臂浇注施工；不需大量施工支架和大型临时设备，不受跨数限制，桥梁施工受力状态与运营受力状态基本相近.采用挂篮悬臂浇注施工；不需大量施工支架和大型临时设备，不受跨数限制，桥梁施工受力状态与运营受力状态基本相近.5桥型特点 主墩无支座，施工无体系转换，伸缩缝少，行车舒适性好，顺桥向抗弯刚度和横向抗扭刚度大，受力性能好.顺桥向抗推刚度小，故能有效地减小温度、混凝土收缩徐变和地震影响.有利于养护维修.结构受力性能好，变形小，伸缩缝少，行车平顺舒适，造型简洁美观，养护工程量小，抗震能力强.主墩有支座，顺桥向抗弯刚度和横桥向抗扭刚度小，不利于悬臂施工的横向抗风要求.结构受力性能好，变形小，伸缩缝少，行车平顺舒适，造型简洁美观，养