The Structure of Concrete Bridge
Pre-stressed concrete has proved to be technically advantageous, economically competitive, and esthetically superior bridges, from very short span structures using standard components to cable-stayed girders and continuous box girders with clear spans of nearly 100aft .Nearly all concrete bridges, even those of relatively short span, are now pre-stressed. Pre-casting, cast-in-place construction, or a combination of the two methods may be used .Both pre-tensioning and post tensioning are employed, often on the same project.
In the United States, highway bridges generally must-meet loading ,design ,and construction requirements of the AASHTO Specification .Design requirements for pedestrian crossings and bridges serving other purposes may be established by local or regional codes and specifications .ACI Code provisions are often incorporated by reference .
Bridges spans to about 100ft often consist of pre-cast integral-deck units ,which offer low initial cost ,minimum ,maintenance ,and fast easy construction ,with minimum traffic interruption .Such girders are generally pre-tensioned .The units are placed side by side ,and are often post-tensioned laterally at intermediate diaphragm locations ,after which shear keys between adjacent units are filled with non-shrinking mortar .For highway spans ,an asphalt wearing surface may be applied directly to the top of the pre-cast concrete .In some cases ,a cast-in-place slab is placed to provide composite action .
The voided slabs are commonly available in depths from 15 to 21 in .and widths of 3 to 4 ft .For a standard highway HS20 loading, they are suitable for spans to about 50 ft, Standard channel sections are available in depths from 21 to 35 in a variety of widths, and are used for spans between about 20 and 60 ft .The hollow box beams-and single-tee girders are intended for longer spans up to about 100 ft.
For medium-span highway bridges ,to about 120 ft ,AASHTO standard I beams are generally used .They are intended for use with a composite cast-in-place roadway slab .Such girders often combine pre-tensioning of the pre-cast member with post-tensioning of the composite beam after the deck is placed .In an effort to obtain improved economy ,some states have adopted more refined designs ,such as the State of Washington standard girders.
The specially designed pre-cast girders may be used to carry a monorail transit system .The finished guide way of Walt Disney World Monorail features a series of segments, each consisting of six simply supported pre-tensioned beams ,together to from a continuous structure .Typical spans are 100 to 110 ft . Approximately half of the 337 beams used have
some combination of vertical and horizontal curvatures and variable super elevation .All beams are hollow, a feature achieved by inserting a styro-foam void in the curved beams and by a moving mandrel in straight beam production.
Pre-cast girders may not be used for spans much in excess of 120 ft because of the problems of transporting and erecting large, heavy units.
On the other hand ,there is a clear trend toward the use of longer spans for bridges .For elevated urban expressways ,long spans facilitate access and minimize obstruction to activities below .Concern for environmental damage has led to the choice of long spans for continuous viaducts . For river crossings, intermediate piers may be impossible because of requirements of navigational clearance.
In typical construction of this type, piers are cast-in-place, often using the slip-forming technique .A ―hammerhead‖ section of box girder is often cast at the top of the pier, and construction proceeds in each direction by the balanced cantilever method. Finally, after the closing cast-in-place joint is made at mid-span, the structure is further post-tensioned for full continuity .Shear keys may be used on the vertical faces between segments, and pre-cast are glued with epoxy resin.
The imaginative engineering demonstrated by many special techniques has extended the range of concrete construction for bridges far beyond anything that could be conceived just a few years ago .In the United States, twin curved cast-in –place segmental box girders have recently been completed for of span of 310 ft over the Eel River in northern California .Preliminary design has been completed for twin continuous box girders consisting of central 550 ft spans flanked by 390 ft side spans.
Another form of pre-stressed concrete bridge well suited to long spans is the cable-stayed box girder .A notable example is the Chaco-Corrientes Bridge in Argentina .The bridges main span of 804 ft is supported by two A-frame towers, with cable stays stretching from tower tops to points along the deck .The deck itself consists of two parallel box girders made of pre-cast sections erected using the cantilever method .The tensioned cables not only provide a vertical reaction component to support the deck ,but also introduce horizontal compression to the box girders ,adding to the post-tensioning force in those members .
Stress-ribbon Bridge pioneered many years ago by the German engineer Ulrich Finsterwalder. The stress-ribbon bridge carries a pipeline and pedestrians over the Rhine River with a span of 446 ft .The superstructure erection sequence was to (a) erect two pairs of cables, (b) place pre-cast slabs forming a sidewalk deck and a U under each of the sets of cables, and (c) cast-in-place concrete within the two Us. The pipeline is placed atop supports at railing height, off to one side, which greatly increases the wind speed of the structure.
It is appropriate in discussing bridge forms to mention structural esthetics .The time is past when structures could be designed on the basis of minimum cost and technical advantages alone .Bridge structures in particular are exposed for all to see .To produce a structure that is visually offensive ,as has occurred all too often in the past, is an act professional irresponsibility .Particularly for major spans ,but also for more ordinary structures ,architectural advice should be sought early in conceptual stage of the design process.
混凝土梁桥的结构形式
事实证明，预应力混凝土结构是在技术上先进、经济上有竞争力、符合审美学的一种先进技术。从使用标准组成的小跨径桥梁到吊梁和跨径将近100英尺的连续箱梁桥，几乎所有的混凝土桥梁，甚至于相对短时间的桥梁都是预应力结构的。采用预制、现场浇筑或两种方法并用。在同一工程中经常同时使用先张法和后张法。
在美国，公路桥一般情况下必须满足荷载、设计和AASHTO规定的建设的要求。对于服务于其它目的步行街和桥梁的设计要求由当地的或地方的代码建立。ACI代码的备注也被纳入参考。
伴随最小交通中断的大约100英尺的跨径的桥梁由提供低的初级预算，最小量维修和养护费用和快速的简易的预制板组成。这种梁一般是用先张法。预制板一块挨一块的放置并且在相邻的预制板间受剪的缝隙填满不收缩的灰泥之后，经常在中间横膈膜的位置后张拉。对于公路，用沥青铺设的表面可以直接用在预制混凝土的上面。在某些情况下，一块放置在正确位置的现浇板提供复合作用。
空心板一般用于深度15英尺到21英尺，宽度3英尺或4英尺。对于一个标准HS20的公路，空心板适合于大约50 英尺的跨径。标准渠化区段在多种宽度，深度从21英尺到35英尺时是有利的，可用于大约20英尺到60英尺的跨径。中空的箱形梁和T形梁用于大约100英尺的长跨径。
对于中等跨径的大约120英尺的公路桥，一般使用AASHTO 标准梁。它们和一种复合现场预制行车道板一起使用。在板被安置之后，这样的梁经常在预浇梁的先张拉与合成梁的后张拉后结合。试图获得改进经济，一些国家已经采用更精炼的设计，例如华盛顿州标准梁。
经过特别设计预制建筑梁可以用来携带一个单轨铁路系统。完成的沃尔特迪斯尼乐园单轨铁路的一系列的特征, 每个包括六个单独支持的预拉梁，一起形成连续结构。典型的跨距是100到110英尺。被使用的337根梁，大约一半有垂直与水平曲率和易变超级升高的一些结合。所有的梁是中空的，它的特征是通过在曲梁中插入泡沫和在直梁制作中移动形心轴获得。
由于运输问题和构件垂直的大而重的问题，预制梁不能用于跨径超过120英尺的桥梁。另一方面，桥梁有一种向大跨径发展的明显趋势。对于提高的都市高速道路来说，大跨径促进通路而且将对下面的活动妨碍减到最少。对环境的损害问题的关心，导致连续高架桥大跨径的选择。对于跨河桥，因为航行间隙的需求，中间可能不可以搭设桥墩。
在这一个类型的典型建筑中，桥墩（台）采用现场预制, 经常使用滑动的技术。一个箱梁的" 锤头"浇筑在桥墩的顶端, 并且通过平衡的悬臂方法控制每个方向的建筑进行。最后,在完成跨中结合处的浇筑之后, 这种结构对于完全连续性的桥梁来说是进一步
的受拉的。修剪钥匙可能被用在片段之间垂直面之上, 而且预制建筑与环氧基树脂黏在一起。
想象的工程学藉着许多特别的技术示范已经延长混凝土建筑的范围，就桥梁而言，已经远远超过几年以前可以想象的到的任何事。在美国，双向弯曲的现场浇铸的部分箱梁已经成功地完成310 英尺的跨距，跨越了北加州的鳗鱼河。该桥的中间跨度550英尺，侧跨跨度390英尺，初步设计已经完成。
预应力混凝土桥梁很适合于大跨径的另一种形式是悬索箱梁。一个值得注意的例子是阿根廷境内的Chaco-Corrientes桥。桥的主跨径804英尺，由两个A型构架塔支撑，悬索从塔顶到沿着底板伸展。受拉的悬索不仅提供一种垂直反应组成支撑底板，而且对于箱梁产生水平的压缩，增加构件中的张拉力。
许多年以前德国工程师Ulrich Finsterwalder 提出适合于负担荷载和大跨径的一个结构类型是压带式桥。压带是桥运输跨越莱茵河的一个管道和人行道，跨径446英尺。上部结构的施工顺序是（a）垂直的一对悬索，(b)在每个悬索的下面，安置预制板形成一人行道甲板和一U型的平台, 并且(c)在附近现场浇注混凝土。放置在顶部的管道支撑在扶手的顶部，向一边倾斜，大幅地增加结构的主要风速。
讨论桥梁形式应适当的考虑结构的美学。当结构可能根据最小的费用和技术设计的时候，时间消逝了。特别是桥梁结构到处可见。生产视觉上不愉快的结构, 过去经常发生, 是一种不负专业责任的行为。特别地对于主要的跨距，还有一些比较普通的结构来说，应该在设计过程的概念阶段寻找建筑的建议。
出处：
安瑞克．混凝土桥梁结构形式[J]．建筑实录(美)，2010，33(36)：34—36
Concrete, Reinforced Concrete, and PrestressedConcrete Concrete is a stone like material obtained by permitting a carefully proportioned mixture of cement, sand and gravel or other aggregate, and water to harden in forms of the shape and dimensions of the desired structure. The bulk of the material consists of fine and coarse aggregate. Cement and water interact chemically to bind the aggregate particles into a solid mass. Additional water, over and above that needed for this chemical reaction, is necessary to give the mixture workability that enables it to fill the forms and surround the embedded reinforcing steel prior to hardening. Concretes with a wide range of properties can be obtained by appropriates adjustment of the proportions of the constituent materials. Special cements, special aggregates, and special curing methods permit an even wider variety of properties to be obtained. These properties depend to a very substantial degree on the proportions of the mix, on the thoroughness with which the various constituents are intermixed, and on the conditions of humidity and temperature in which the mix is maintained from the moment it is placed in the forms of humidity and hardened. The process of controlling conditions after placement is known as curing. To protect against the unintentional production of substandard concrete, a high degree of skillful control and supervision is necessary throughout the process, from the proportioning by weight of the individual components, trough mixing and placing, until the completion of curing. The factors that make concrete a universal building material are so pronounced that it has been used, in more primitive kinds and ways than at present, for thousands of years, starting with lime mortars from 12,000 to 600 B.C. in Crete, Cyprus, Greece, and the Middle East. The facility with which , while plastic, it can be deposited and made to fill forms or molds of almost any practical shape is one of these factors. Its high fire and weather resistance are evident advantages. Most of the constituent materials, with the exception of cement and additives, are usually available at low cost locally or at small distances from the construction site. Its compressive strength, like that of natural stones, is high, which makes it suitable for members primarily subject to compression, such as columns and arches. On the other hand, again as in natural stones, it is a relatively brittle material whose tensile strength is small compared with its compressive strength. This prevents its economical use in structural members that ate subject to tension either entirely or over part of their cross sections. To offset this limitation, it was found possible, in the second half of the
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学校 毕业设计（论文）附件 外文文献翻译 学号： xxxxx 姓名： xxx 所在系别： xxxxx 专业班级： xxx 指导教师： xxxx 原文标题： Building construction concrete crack of prevention and processing 2012年月日 .
建筑施工混凝土裂缝的预防与处理1 摘要 混凝土的裂缝问题是一个普遍存在而又难于解决的工程实际问题，本文对混凝土工程中常见的一些裂缝问题进行了探讨分析，并针对具体情况提出了一些预防、处理措施。 关键词：混凝土裂缝预防处理 前言 混凝土是一种由砂石骨料、水泥、水及其他外加材料混合而形成的非均质脆性材料。由于混凝土施工和本身变形、约束等一系列问题，硬化成型的混凝土中存在着众多的微孔隙、气穴和微裂缝，正是由于这些初始缺陷的存在才使混凝土呈现出一些非均质的特性。微裂缝通常是一种无害裂缝，对混凝土的承重、防渗及其他一些使用功能不产生危害。但是在混凝土受到荷载、温差等作用之后，微裂缝就会不断的扩展和连通，最终形成我们肉眼可见的宏观裂缝，也就是混凝土工程中常说的裂缝。 混凝土建筑和构件通常都是带缝工作的，由于裂缝的存在和发展通常会使内部的钢筋等材料产生腐蚀，降低钢筋混凝土材料的承载能力、耐久性及抗渗能力，影响建筑物的外观、使用寿命，严重者将会威胁到人们的生命和财产安全。很多工程的失事都是由于裂缝的不稳定发展所致。近代科学研究和大量的混凝土工程实践证明，在混凝土工程中裂缝问题是不可避免的，在一定的范围内也是可以接受的，只是要采取有效的措施将其危害程度控制在一定的范围之内。钢筋混凝土规范也明确规定：有些结构在所处的不同条件下，允许存在一定宽度的裂缝。但在施工中应尽量采取有效措施控制裂缝产生，使结构尽可能不出现裂缝或尽量减少裂缝的数量和宽度，尤其要尽量避免有害裂缝的出现，从而确保工程质量。 混凝土裂缝产生的原因很多，有变形引起的裂缝：如温度变化、收缩、膨胀、不均匀沉陷等原因引起的裂缝；有外载作用引起的裂缝；有养护环境不当和化学作用引起的裂缝等等。在实际工程中要区别对待，根据实际情况解决问题。 混凝土工程中常见裂缝及预防: 1.干缩裂缝及预防 干缩裂缝多出现在混凝土养护结束后的一段时间或是混凝土浇筑完毕后的一周左右。水泥浆中水分的蒸发会产生干缩，且这种收缩是不可逆的。干缩裂缝的产生主要是由于混凝土内外水分蒸发程度不同而导致变形不同的结果：混凝土受外部条件的影响，表面水分损失过快，变形较大，内部湿度变化较小变形较小，较大的表面干缩变形受到混凝土内部约束，产生较大拉应力而产生裂缝。相对湿度越低，水泥浆体干缩越大，干缩裂缝越易产 1原文出处及作者：《加拿大土木工程学报》
土木外文翻译--高温下钢筋混凝土中钢筋的性能
外文原文： Research Letters in Materials Science Volume 2008 (2008), Article ID 814137, 4 pages doi:10.1155/2008/814137 Research Letter Properties of Reinforced Concrete Steel Rebars Exposed to High Temperatures ?lker Bekir Top?u and Cenk Karakurt Department of Civil Engineering, Eski?ehir Osmangazi University, 26480 Eski?ehir, Turkey Received 12 February 2008; Accepted 31 March 2008 Academic Editor: Rajiv S. Mishra Copyright ? 2008 ?lker Bekir Top?u and Cenk Karakurt. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The deterioration of the mechanical properties of yield strength and modulus of elasticity is considered as the primary element affecting the performance of steel structures under fire. In this study, hot-rolled S220 and S420 reinforcement steel rebars were subjected to high temperatures to investigate the fire performance of these materials. It is aimed to determine the remaining mechanical properties of steel rebars after elevated temperatures. Steels were subjected to 20, 100, 200, 300, 500, 800, and 9 5 0 ° C temperatures for 3 hours and tensile tests were carried out. Effect of temperature on mechanical behavior of S220 and S420 were determined. All mechanical properties were reduced due to the temperature increase of the steel rebars. It is seen that mechanical properties of S420 steel was influenced more than S220 steel at elevated temperatures.
毕业设计（论文）外文参考文献及译文 英文题目Component-based Safety Computer of Railway Signal Interlocking System 中文题目模块化安全铁路信号计算机联锁系统 学院自动化与电气工程学院 专业自动控制 姓名葛彦宁 学号 200808746 指导教师贺清 2012年5月30日
Component-based Safety Computer of Railway Signal Interlocking System 1 Introduction Signal Interlocking System is the critical equipment which can guarantee traffic safety and enhance operational efficiency in railway transportation. For a long time, the core control computer adopts in interlocking system is the special customized high-grade safety computer, for example, the SIMIS of Siemens, the EI32 of Nippon Signal, and so on. Along with the rapid development of electronic technology, the customized safety computer is facing severe challenges, for instance, the high development costs, poor usability, weak expansibility and slow technology update. To overcome the flaws of the high-grade special customized computer, the U.S. Department of Defense has put forward the concept：we should adopt commercial standards to replace military norms and standards for meeting consumers’demand [1]. In the meantime, there are several explorations and practices about adopting open system architecture in avionics. The United Stated and Europe have do much research about utilizing cost-effective fault-tolerant computer to replace the dedicated computer in aerospace and other safety-critical fields. In recent years, it is gradually becoming a new trend that the utilization of standardized components in aerospace, industry, transportation and other safety-critical fields. 2 Railways signal interlocking system 2.1 Functions of signal interlocking system The basic function of signal interlocking system is to protect train safety by controlling signal equipments, such as switch points, signals and track units in a station, and it handles routes via a certain interlocking regulation. Since the birth of the railway transportation, signal interlocking system has gone through manual signal, mechanical signal, relay-based interlocking, and the modern computer-based Interlocking System. 2.2 Architecture of signal interlocking system Generally, the Interlocking System has a hierarchical structure. According to the function of equipments, the system can be divided to the function of equipments; the system
废弃混凝土再生新技术探索 【摘要】本文对目前废弃混凝土再生技术的研究做了论述,并指出了其中存在的一些问题。结合混凝土各组成部分的结构特点,提出了通过低温煅烧对废弃混凝土综合利用的新方法。在750℃温度条件下煅烧1h,可以实现水泥浆与骨料的分离。脱水后的水泥浆可以重新获得水化活性。得到的混凝土骨料可以满足使用要求。 【关键词】废弃混凝土;再生技术;煅烧;水化活性;压碎指标 【中图分类号】TU352·8【文献标识码】A【文章编号】1001-6864(2009)09-0004-02 国家“十五计划”纲要指出:“坚持资源开发与节约并举,把节约放在首位,法保护和合理使用资源,提高资源利用率,实现永续利用。推进资源综合利用技术研究开发,加强废旧物资回收利用,加快废弃物处理的产业化,促进废弃物转化为可用资源。”保护环境、节约能源、减少废料、以持续的方式使用可再生资源是可持续发展战略的重要内容。建材工业是典型的基础原料工业,在国民经济发展中具有重要作用。建材工业又是典型的资源、能源消耗型工业,在其快速发展的同时,面临着资源、能源的过度消耗和环境的严重污染。建筑和建材行业的根本出路就是走可持续发展的道路[1]。起初,我国对混凝土的利用仅是简单的破碎充当再生粗骨料,这种生产的再生骨料性能与天然粗骨料的性能存在一定差异,主要表现在密度低、吸水率高、压碎指标大,表明再生骨料的空隙率高,强度低,这主要是由于其表面附着有大量水泥砂浆及在破碎过程中引入一定量的微裂纹的缘故[2],生成的混凝土性能低,耐久性、抗冻融、抗腐蚀能力差。研究者根据再生骨料再利用过程中存在的问题,对再生骨料进行了物理、化学改性以及整形改性。如朱崇绩等通过整形除去再生骨料表面的砂浆,使颗粒变得光滑,需水量降低,使所配制的混凝土收缩降低,但仍高于天然骨料混凝土[3]。没有解决再生骨料中微裂纹带来的弊端。目前有研究者对废弃混凝土进行了综合利用研究,通过筛分获得砌筑砂浆或进步筛分生产具有水化活性的再生水泥。如孙荣光等[4]对旧水泥浆高温处理后的再水化胶凝特性研究,得出再生水泥具有再水化的能力,同时生成C-S-H凝胶、Aft和CH等物质,说明水化产物结构相同,但由于大量脱水相的存在使水化速度快。余睿等[5]通过对水泥浆的研究得出石膏和粉煤灰组成改性剂能延长活化水泥浆的初凝时间,增强其抗压强度,但不能减少活化水泥浆的标准稠度需水量。由于易水化的水泥石脱水需要时间,所以煅烧时间和脱水温度对再生水泥性能不容忽视。 1．废弃混凝土裂解温度确定 混凝土是由水泥、粗细集料、矿物掺合料等加水拌合,经水化硬化而形成的一种微观不均匀,宏观均匀的人造石。废弃混凝土在低温煅烧时的温度由水泥脱水温度与石灰石分解温度共同决定。 1·1水泥水化产物脱水温度 文献认为,含水矿物中普通吸附水的脱水温度一般为100~110℃,存在于层状硅酸盐结构中的层间水或胶体矿物中的胶体水多数要在200~300℃以内脱水,个别要在400℃以内脱水;架状结构的硅酸盐结构水则要在400℃左右才大量脱出。结晶水在不同结构中的矿物中结合程度不同,其脱水温度也不同。结构水是矿物中结合最牢的水,脱水温度较高,一般要在450℃以上才脱水[5]。为了确定废弃混
随时间变化的钢筋混凝土阻力分析外文翻译 Prepared on 24 November 2020
毕业设计(论文)外文资料翻译 系（部）：建筑工程系 专业：土木工程 班级： B070704 姓名： 123 学号： 123 外文出处：Journal of Wuhan University 附件： 1. 原文； 2. 译文 2010年12月29日 附件1：原文 随时间变化的钢筋混凝土阻力分析 摘要∶对钢筋混凝土材料时间相关性的分析方法进行介绍，讨论钢筋混凝土的作用 机理，然后再研究随时间而定的钢筋混凝土抵抗力。此外，钢筋混凝土结构中的钢材腐 蚀也是需要被分析的。鉴定随时间而变的抵抗力的实际统计方法，包括物质的材料，结 构尺寸，影响计算的确定。另外，范例中估计随时间而变钢筋混凝土结构构件的抵抗力 是给的。 关键字∶不定分析；随时间变化的抵抗力；钢筋混凝土 1．介绍： 因为钢筋混凝土材料适用于很多地方，并且价格便宜，所以它在土木工程中是一种 非常有用的材料。因此，这种材料大量的被使用。然而，传统的建筑结构设计和钢筋混
凝土材料的研究很少注意到钢筋混凝土强度和时间的关系，尤其是作用在材料上的不同影响作用几乎是不予研究的。直到近年来，在建筑施工中的一些研究才涉及这个问题——关于钢筋混凝强度与时间相关性的。已做过的关于钢筋混凝土柱破坏概率的研究表明低强度的钢筋混凝土柱破坏概率低于偶然的荷载作用下的破坏概率。并且这种计算方法已经被运用到随时间而变化的破坏概率的计算上。低强度的和Liu[4] 混凝土结构耐久性上的研究认为这种作用加速了其的破坏。并且Lu [6]等已经论述钢筋腐蚀的情况。一般而言，依赖不同因素的钢筋混凝土抵抗力明显减小。在对混凝土结构安全性校核上,基础理论为钢筋混凝土耐久性分析提供了建议。研究随时间而变的钢筋混凝土结构的性质的是必要的。 ２．影响钢筋混凝土机理的因素 许多因素对钢筋混凝土抵抗力都产生影响。在水区域内存在着超过50种化学腐蚀元素,水在其中工作并且起调节作用。获得一次相关钢筋混凝土模型的实际方法是一种多因素理解方法。通常，对于单一的因素，许多结果只考虑到混凝土的碳化作用，碳化的厚度可以用下面公式来表示： 可以写为：D ( t) = K t (1) 式中D ( t)，K和t分别为厚度，速度系数与碳化的时间。 到目前为止，虽然有许多模型被运用到钢筋的断裂，疲劳破坏中，但是还没有大家都认可的结论存在。一般而言，能够降低钢筋混凝土的抵抗力的变量有钢筋的几何尺寸，周边环境情况以及随时间而变的抵抗力等。显而易见，钢筋混凝土抵抗力的变化是的一个随机函数过程或者说是一系列材料和结构变量的相互作用。钢筋混凝土在空气中的碳化被称之为中和反应。它是合成物与在空中的CO2以及钢筋混凝土中的碱性材料缓慢中和的过程。在空气中完全地碳化密实混凝土中的钢筋保护层需要花费几十年的时
桥梁结构 桥梁起源 第一座人工桥梁是由横架在河流上的树干或者平石而形成的。毫无疑问，它比基督的诞生还要早几千年建成。甚至在此之前，古人一定惊讶于，在Ardeche 会有跨度为194英尺、高度为111英尺的Pont d’Arc这样的天然拱桥横跨河流。但是随着时间的流逝，一些先驱者将两块石头横跨狭窄的小溪并堵在一起形成倒置的“V”形，从而建成了第一座拱桥。 据degrand所言，有所记载的最早的桥是在大约公元前2650年，由埃及的第一任国王Menes在尼罗河上修建的，但是没有更多的细节描述。Diodorus Siculus提供了另外一座5个世纪后建成的桥梁的详细资料，它是由巴比伦皇后Semiramis在幼发拉底河上建成的。Herodotus将这座桥视为女王统治Nitocris5个世纪的原因。首先，河流在经过城市时转向流入一个人工湖，使桥墩可以修建在干燥的河床上。桥墩的石头采用铁条焊接在一起。甲板是由不低于30英尺宽的木材、雪松、松柏、棕榈修建的，部分甲板是可移动的，每晚拿掉用来防止土匪。当桥建成后，河水再被引回到原来的河道。因此今天还存在一些记录，多少是真实的，多少是随着时间的流逝使我们永远不知道的，但毫无疑问，在4000年前的巴比伦有一座不同寻常的桥。 桥梁类型 我们只能推测这些起源。我们知道古代的吊桥是用扭曲的藤蔓绑在峡谷两侧的树干上形成的，就像一张充满危险的悬挂着的蜘蛛网。但是桥梁型式什么时候得到发展，或者第一座桥是什么型式的，我们都不能肯定。我们只知道三种桥梁类型：板梁桥（在河流上架设一根树干）、拱桥、吊桥，它们在有所记载的早期就开始被建造了。最常见的板梁桥被称为跨桥，如果两个或者更多的梁相连修建在桥墩上就会连在一起形成跨桥，或者是修建成悬臂桥。然而，他们仅是不同类型的板梁桥而已，并不是其他类型的桥梁。改变梁、拱、悬架这三种型式并使其相互结合来共同适应建筑物结构的受力要求，数年来，建筑材料已经越来越普及，涉及到木材、石头，人工材料如砖、水泥、铁和钢材。 板梁桥 一个简单的单跨桥可能是钢结构（可能是板梁），钢筋混凝土或预应力钢筋混凝土。一个钢结构简支桥梁的最大跨度通常约为100英尺（虽然更成长跨度的桥梁已经建成）。然而，当跨度很大时，通常采用连续梁。在德国有一个中央跨度为354英尺、边跨为295英尺的板梁桥。 对于约150英尺的支墩之间的梁，通常采用桁架，并且钢材是必不可少的。1917年，在伊利诺斯州的俄亥俄河上修建了一座跨度为720英尺的简支桥。 无论有没有悬跨，悬臂桥的布置原则就是在桥墩建成后，在桥墩上架设桥梁。两个桥墩之间的部分称为悬跨，通常是先放在一个预制单元，再架在适当位置。因此，这种型式的桥梁是从悬臂的两端用两条锚固的悬臂来支撑桥梁的。桥墩中间的弯矩和剪力最大，在这些位置通常要求桥墩埋设的更深。 当桥的跨度很大时，就要求桥要有更好的强度，悬臂桥通常采用钢桁架结构（桁梁）。这种型式可以使桥墩间的跨度达到约1800英尺。尽管这座桥看起来像是拱桥，事实上它是双悬臂桁架梁。我们会注意到悬臂桥上的最高强度设计在主墩处，因为这些地方可能有最大应力产生。
Inventory management Inventory Control On the so-called "inventory control", many people will interpret it as a "storage management", which is actually a big distortion. The traditional narrow view, mainly for warehouse inventory control of materials for inventory, data processing, storage, distribution, etc., through the implementation of anti-corrosion, temperature and humidity control means, to make the custody of the physical inventory to maintain optimum purposes. This is just a form of inventory control, or can be defined as the physical inventory control. How, then, from a broad perspective to understand inventory control? Inventory control should be related to the company's financial and operational objectives, in particular operating cash flow by optimizing the entire demand and supply chain management processes (DSCM), a reasonable set of ERP control strategy, and supported by appropriate information processing tools, tools to achieved in ensuring the timely delivery of the premise, as far as possible to reduce inventory levels, reducing inventory and obsolescence, the risk of devaluation. In this sense, the physical inventory control to achieve financial goals is just a means to control the entire inventory or just a necessary part; from the perspective of organizational functions, physical inventory control, warehouse management is mainly the responsibility of The broad inventory control is the demand and supply chain management, and the whole company's responsibility. Why until now many people's understanding of inventory control, limited physical inventory control? The following two reasons can not be ignored: First, our enterprises do not attach importance to inventory control. Especially those who benefit relatively good business, as long as there is money on the few people to consider the problem of inventory turnover. Inventory control is simply interpreted as warehouse management, unless the time to spend money, it may have been to see the inventory problem, and see the results are often very simple procurement to buy more, or did not do warehouse departments . Second, ERP misleading. Invoicing software is simple audacity to call it ERP, companies on their so-called ERP can reduce the number of inventory, inventory control, seems to rely on their small software can get. Even as SAP, BAAN ERP world, the field of
英文译文 在桥梁覆盖中的聚丙烯酰胺改性混凝土在实验室材料性能测试和有 限元建模结构中的反应 Qinwu Xu1; Zengzhi Sun2; Hu Wang3; and Aiqin Shen4 摘自： Qinwu https://www.doczj.com/doc/739338040.html,boratory Testing Material Property and FE Modeling Structural Response of PAM-Modified Concrete Overlay on Bridges[J]. ASCE:Journal of bridge engineering,2009,14(1):26-35 摘要： 在开裂困扰和界面脱粘的影响下，波特兰水泥混凝土通过反复装载车辆和温度循环进行覆盖桥面。为了提高覆盖性能，本研究运用聚丙烯酰胺聚合物能修改混凝土力学的性能。直接剪切和耐冲击性试验，旨在分别衡量界面结合强度和动态性能。弯曲强度和弯曲疲劳根据标准进行试验。同时，在交通的负荷下，为了分析应激反应和提高结构设计，建立T梁和箱梁桥三维有限元模型，通过一个分析模型弯曲应力的开发来验证有限元模拟结果。在有限元模型设计中，橡胶垫能够吸收弯曲应力。实验室测试结果表明，聚丙烯酰胺可以显著提高混凝土的抗折强度，粘结强度，耐冲击和疲劳寿命。含8％聚丙烯酰胺的改性混凝土对水泥质量比混凝土与其他PAM的百分比提出了更高的抗弯强度和耐冲击性。有限元模拟结果表明，一个关键覆盖厚度的存在能够减小在结构设计中应该避免的最大界面剪应力，橡胶垫能够有效地减轻弯曲应力。 关键词：桥梁；化验结果；有限元法；材料特性；结构响应；波特兰水泥；混凝土 导言 波特兰水泥混凝土已被用于桥面表面结构的覆盖，以支持车辆装载和保护桥梁结构。在反复车辆装载，温度循环，收缩和化学反应的影响下桥梁的覆盖可能遇到开裂的
中英文翻译
原文： DESIGN OF REINFORCED CONCRETE STRUCTURES 1. BASIC CONCERPTS AND CHARACERACTERISTICS OF REINFORCED CONCRETE Plain concrete is formed from hardened mixture of cement, water , fine aggregate , coarse aggregate (crushed stone or gravel ) , air and often other admixtures . The plastic mix is placed and consolidated in the formwork, then cured to accelerate of the chemical hydration of hen cement mix and results in a hardened concrete. It is generally known that concrete has high compressive strength and low resistance to tension. Its tensile strength is approximately one-tenth of its compressive strength. Consequently, tensile reinforcement in the tension zone has to be provided to supplement the tensile strength of the reinforced concrete section. For example, a plain concrete beam under a uniformly distributed load q is shown in Fig . 1.1(a), when the distributed load increases and reaches a value q=1.37KN/m , the tensile region at the mid-span will be cracked and the beam will fail suddenly . A reinforced concrete beam if the same size but has to steel reinforcing bars (2φ16) embedded at the bottom under a uniformly distributed load q is shown in Fig.1.1(b). The reinforcing bars take up the tension there after the concrete is cracked. When the load q is increased, the width of the cracks, the deflection and the stress of steel bars will increase . When the steel approaches the yielding stress ?y , the deflection and the cracked width are so large offering some warning that the compression zone . The failure load q=9.31KN/m, is approximately 6.8 times that for the plain concrete beam. Concrete and reinforcement can work together because there is a sufficiently strong bond between the two materials, there are no relative movements of the bars and the surrounding concrete cracking. The thermal expansion coefficients of the two materials are 1.2×10-5K-1 for steel and 1.0×10-5~1.5×10-5K-1 for concrete . Generally speaking, reinforced structure possess following features : Durability .With the reinforcing steel protected by the concrete , reinforced concrete