桥式起重机桥架结构设计

桥式起重机桥架结构设计,桥式起重机,结构设计 *学院毕业设计任务书系 别：机械工程系专 业：机械设计制造及其自动化学 生 姓 名：学 号：设计题目：桥式起重机桥架结构设计起 迄 日 期:设计地点:指 导 教 师:系 主 任:发任务书日期: 年 月 日毕 业 设 计 任 务 书1毕业设计课题的任务和要求： 熟悉桥式起重机的结构和工作原理，完成某型号桥式起重机的结构设计计算，并利用Solidwork建立其关键件的三维模型和工程图，相关参数依据起重机设计手册。 2毕业设计课题的具体工作内容（包括原始数据、技术要求、工作要求等）：1 掌握Solidworks的使用技术；2 熟悉桥式起重机的工作原理；3 完成某型号桥式起重机的结构设计计算；4 完成桥式起重机的的三维建模，绘制关键零部件的二维工程图； 5 撰写设计说明书： (1)设计合理，语句通顺，格式规范，图表正确，表述清晰； (2)打印成册。6 外文翻译。毕 业 设 计 任 务 书3对毕业设计课题成果的要求包括毕业设计、图纸、实物样品等)：1 毕业设计说明书一本；2 图纸一套。4毕业设计课题工作进度计划：起 迄 日 期工 作 内 容2013年2月25日 3 月 23 日3月 24日 5月 9 日5月 10日 5月25日5月 25日 6月10日学习相关软件，查阅资料，撰写开题报告；熟悉开发环境，详细设计；撰写论文；论文答辩。学生所在系审查意见：系主任： 年 月 日 *学院*届毕业设计中英文翻译The Use and History of CraneEvery time we see a crane in action we remains without words, these machines are sometimes really huge, taking up tons of material hundreds of meters in height. We watch with amazement and a bit of terror, thinking about what would happen if the load comes off or if the movement of the crane was wrong. It is a really fascinating system, surprising both adults and children. These are especially tower cranes, but in reality there are plenty of types and they are in use for centuries. The cranes are formed by one or more machines used to create a mechanical advantage and thus move large loads. Cranes are equipped with a winder, a wire rope or chain and sheaves that can be used both to lift and lower materials and to move them horizontally. It uses one or more simple machines to create mechanical advantage and thus move loads beyond the normal capability of a human. Cranes are commonly employed in the transport industry for the loading and unloading of freight, in the construction industry for the movement of materials and in the manufacturing industry for the assembling of heavy equipment.1. OverviewThe first construction cranes were invented by the Ancient Greeks and were powered by men or beasts of burden, such as donkeys. These cranes were used for the construction of tall buildings. Larger cranes were later developed, employing the use of human treadwheels, permitting the lifting of heavier weights. In the High Middle Ages, harbor cranes were introduced to load and unload ships and assist with their construction - some were built into stone towers for extra strength and stability. The earliest cranes were constructed from wood, but cast iron and steel took over with the coming of the Industrial Revolution.For many centuries, power was supplied by the physical exertion of men or animals, although hoists in watermills and windmills could be driven by the harnessed natural power. The first mechanical power was provided by steam engines, the earliest steam crane being introduced in the 18th or 19th century, with many remaining in use well into the late 20th century. Modern cranes usually use internal combustion engines or electric motors and hydraulic systems to provide a much greater lifting capability than was previously possible, although manual cranes are still utilized where the provision of power would be uneconomic.2. HistoryAncient GreeceThe crane for lifting heavy loads was invented by the Ancient Greeks in the late 6th century BC. The archaeological record shows that no later than c.515 BC distinctive cuttings for both lifting tongs and lewis irons begin to appear on stone blocks of Greek temples. Since these holes point at the use of a lifting device, and since they are to be found either above the center of gravity of the block, or in pairs equidistant from a point over the center of gravity，they are regarded by archaeologists as the positive evidence required for the existence of the crane.The introduction of the winch and pulley hoist soon lead to a widespread replacement of ramps as the main means of vertical motion. For the next two hundred years, Greek building sites witnessed a sharp drop in the weightshandled, as the new lifting technique made the use of several smaller stones more practical than of fewer larger ones. In contrast to the archaic period with its tendency to ever-increasing block sizes, Greek temples of the classical age like the Parthenon invariably featured stone blocks weighing less than 15-20 tons. Also, the practice of erecting large monolithic columns was practically abandoned in favor of using several column drums.Although the exact circumstances of the shift from the ramp to the crane technology remain unclear, it has been argued that the volatile social and political conditions of Greece were more suitable to the employment of small, professional construction teams than of large bodies of unskilled labor, making the crane more preferable to the Greek polis than the more labor-intensive ramp which had been the norm in the autocratic societies of Egypt or Assyria.The first unequivocal literary evidence for the existence of the compound pulley system appears in the Mechanical Problems (Mech. 18， 853a32-853bl3) attributed to Aristotle (384-322 BC), but perhaps composed at a slightly later date. Around the same time, block sizes at Greek temples began to match their archaic predecessors again, indicating that the more sophisticated compound pulley must have found its way to Greek construction sites by then.Ancient RomeThe heyday of the crane in ancient limes came during the Roman Empire, when construction activity soared and buildings reached enormous dimensions. The Romans adopted the Greek crane and developed it further. We are relatively well informed about their lifting techniques.The simplest Roman crane，the Trispastos, consisted of a single-beam jib, a winch, a rope, and a block containing three pulleys. Having thus a mechanical advantage of 3:1, it has been calculated that a single man working the winch could raise 150 kg (3 pulleys x 50 kg = 150), assuming that 50 kg represent the maximum effort a man can exert over a longer time period. Heavier crane types featured five pulleys (Pentaspastos) or, in case of the largest one, a set of three by five pulleys (Polyspastos) and came with two, three or four masts, depending on the maximum load. The Polyspastos, when worked by four men at both sides of the winch，could already lift 3000 kg (3 ropes x 5 pulleys x 4 men x 50 kg = 30(H) kg). In case the winch was replaced by a treadwheel, the maximum load even doubled to 6000 kg at only half the crew, since the treadwheel possesses a much bigger mechanical advantage due to its larger diameter. This meant that, in comparison to the construction of the Egyptian Pyramids, where about 50 men were needed to move a 2.5 ton stone block up the ramp (50 kg per person), the lifting capability of the Roman Polyspastos proved to be 60 times higher (3000 kg per person).However, numerous extant Roman buildings which feature much heavier stone blocks than those handled by the Polyspastos indicate that the overall lifting capability of the Romans went far beyond that of any single crane. At the temple of Jupiter at Baalbek, for instance, the architrave blocks weigh up to 60 tons each，and one corner cornice block even over 100 tons, all of them raised to a height of about 19 m. In Rome, the capital block of Trajans Column weighs 53.3 tons, which had to be lifted to a height of about 34 m (see construction of TrajarTs Column).Middle AgesDuring the High Middle Ages, the treadwheel crane was reintroduced on a large scale after the technology had fallen into disuse in western Europe with the demise of the Western Roman Empire. The earliest reference to a treadwheel (magna rota) reappears in archival literature in France about 1225, followed by an illuminated depiction in a manuscript of probably also French origin dating to 1240. In navigation, the earliest uses of harbor cranes are documented for Utrecht in 1244，Antwerp in 1263，Brugge in 1288 and Hamburg in 1291, while in England the treadwheel is not recorded before 1331.Generally, vertical transport could be done more safely and inexpensively by cranes than by customary methods. Typical areas of application were harbors, mines, and, in particular, building sites where the treadwheel crane played a pivotal role in the construction of the lofty Gothic cathedrals. Nevertheless, both archival and pictorial sources of the time suggest that newly introduced machines like treadwheels or wheelbarrows did not completely replace more labor-intensive methods like ladders, hods and handbarrows. Rather, old and new machinery continued to coexist on medieval construction sites and harbors.Apart from treadwheels, medieval depictions also show cranes to be powered manually by windlasses with radiating spokes, cranks and by the 15th century also by windlasses shaped like a ships wheel. To smooth out irregularities of impulse and get over dead-spots in the lifting process flywheels are known to be in use as early as 1123.The exact process by which the treadwheel crane was reintroduced is not recorded, although its return to construction sites has undoubtedly to be viewed in close connection with the simultaneous rise of Gothic architecture. The reappearance of the treadwheel crane may have resulted from a technological development of the windlass from which the treadwheel structurally and mechanically evolved. Alternatively, the medieval treadwheel may represent a deliberate reinvention of its Roman counterpart drawn from Vitruvius De architectura which was available in many monastic libraries. Its reintroduction may have been inspired，as well，by the observation of the labor-saving qualities of the waterwheel with which early treadwheels shared many structural similarities.Structure and placementThe medieval treadwheel was a large wooden wheel turning around a central shaft with a treadway wide enough for two workers walking side by side. While the earlier compass-arm wheel had spokes directly driven into the central shaft，the more advanced clasp-arnV type featured arms arranged as chords to the wheel rim, giving the possibility of using a thinner shaft and providing thus a greater mechanical advantage.Contrary to a popularly held belief, cranes on medieval building sites were neither placed on the extremely lightweight scaffolding used at the time nor on the thin walls of the Gothic churches which were incapable of supporting the weight of both hoisting machine and load. Rather, cranes were placed in the initial stages of construction on the ground，often within the building. When a new floor was completed, and massive tie beams of the roof connected the walls, the crane was dismantled and reassembled on the roof beams from where it was moved from bay to bay during construction of the vaults. Thus, the crane grew and wandered with the building with the result that today all extant construction cranes in England are found in church towers above the vaulting and below the roof，where they remained after building construction for bringing material for repairs aloft.Harbor usageAccording to the present state of knowledge” unknown in antiquity, stationary harbor cranes are considered a new development of the Middle Ages. The typical harbor crane was a pivoting structure equipped with double treadwheels. These cranes were placed docksides for the loading and unloading of cargo where they replaced or complemented older lifting methods like see-saws, winches and yards.Two different types of harbor cranes can be identified with a varying geographical distribution: While gantry cranes which pivoted on a central vertical axle were commonly found at the Flemish and Dutch coastside, German sea and inland harbors typically featured tower cranes where the windlass and treadwheels were situated in a solid tower with only jib arm and roof rotating. Interestingly, dockside cranes were not adopted in the Mediterranean region and the highly developed Italian ports where authorities continued to rely on the more labor-intensive method of unloading goods by ramps beyond the Middle Ages.Unlike construction cranes where the work speed was determined by the relatively slow progress of the masons, harbor cranes usually featured double treadwheels to speed up loading. The two treadwheels whose diameter is estimated to be 4 m or larger were attached to each side of the axle and rotated together. Today, according to one survey, fifteen treadwheel harbor cranes from pre-industrial times are still extant throughout Europe.28 Beside these stationary cranes, floating cranes which could be flexibly deployed in the whole port basin came into use by the 14th century. RenaissanceMechanical principlesThere are two major considerations in the design of cranes. The first is that the crane must be able to lift a load of a specified weight and the second is that the crane must remain stable and not topple over when the load is lifted and moved to another location.Lifting capacityCranes illustrate the use of one or more simple machines to create mechanical advantage.The lever. A balance crane contains a horizontal beam (the lever) pivoted about a point called the fulcrum. The principle of the lever allows a heavy load attached to the shorter end of the beam to be lifted by a smaller force applied in the opposite direction to the longer end of the beam. The ratio of the loads weight to the applied force is equal to the ratio of the lengths of the longer arm and the shorter ami, and is called the mechanical advantage.The pulley. A jib crane contains a tilted strut (the jib) that supports a fixed pulley block. Cables are wrapped multiple times round the fixed block and round another block attached to the load. When the free end of the cable is pulled by hand or by a winding machine, the pulley system delivers a force to the load that is equal to the applied force multiplied by the number of lengths of cable passing between the two blocks. Thisnumber is the mechanical advantage.The hydraulic cylinder. This can be used directly to lift the load orindirectly to move the jib or beam that carries another lifting device.Cranes，like all machines, obey the principle of conservation of energy. This means that the energy delivered to the load cannot exceed the energy put into the machine. For example, if a pulley system multiplies the applied force by ten, then the load moves only one tenth as far as the applied force. Since energy is proportional to force multiplied by distance, the output energy is kept roughly equal to the input energy (in practice slightly less, because some energy is lost to friction and other inefficiencies).StabilityFor stability, the sum of all moments about any point such as the base of the crane must equate to zero. In practice，the magnitude of load that is permitted to be lifted (called the rated load” in the US) is some value less than the load that will cause the crane to tip (providing a safety margin).Under US standards for mobile cranes, the stability-limited rated load for a crawler crane is 75% of the tipping load. The stability-limited rated load for a mobile crane supported on outriggers is 85% of the tipping load. These requirements, along with additional safety-related aspects of crane design, are established by the American Society of Mechanical Engineers in the volume ASME B30.5-2007 Mobile and Locomotive Cranes.Standards for cranes mounted on ships or offshore platforms are somewhat stricter because of the dynamic load on the crane due to vessel motion. Additionally, the stability of the vessel or platform must be considered.For stationary pedestal or kingpost mounted cranes, the moment created by the boom, jib，and load is resisted by the pedestal base or kingpost. Stress within the base must be less than the yield stress of the material or the cranewill fail.The kinds of crane MobileMain article: Mobile craneThe most basic type of mobile crane consists of a truss or telescopic boom mounted on a mobile platform - be it on road, rail or water.FixedExchanging mobility for the ability to carry greater loads and reach greater heights due to increased stability, these types of cranes are characterized that they, or at least their main structure does not move during the period of use. However，many can still be assembled and disassembled.3. Overhead CranesUseThe most common overhead crane use is in the steel industry. Every step of steel, until it leaves a factory as a finished product, the steel is handled by an overhead crane. Raw materials are poured into a furnace by crane, hot steel is stored for cooling by an overhead crane, the finished coils are lifted and loaded onto trucks and trains by overhead crane, and the fabricator or stamper uses an overhead crane to handle the steel in his factory. The automobile industry uses overhead cranes for handling of raw materials. Smaller workstation cranes handle lighter loads in a work-area, such as CNC mill or saw.HistoryAlton Shaw, of the Shaw Crane Company, is credited with the first overhead crane, in 1874. Alliance Machine, now defunct, holds an AISE citation for one of the earliest cranes as well. This crane was in service until approximately 1980，and is now in a museum in Birmingham, Alabama. Over the years important innovations, such as the Weston load brake (which is now rare) and the wire rope hoist (which is still popular)，have come and gone. The original hoist contained components mated together in what is now called the built-up style hoist. These built up hoists are used for heavy-duty applications such as steel coil handling and for users desiring long life and better durability. They also provide for easier maintenance. Now many hoists are package hoists, built as one unit in a single housing, generally designed for ten-year life or less.第 14页 共 14页起重机的用途与历史每当我们看到一台正在运作的起重机，我们都会惊讶不已，这些机器有时硕大无比，能把成吨的货物提升到空中。看到这些庞然大物的时 候我们心理都带着一种惊愕，有时甚至是有一点恐惧的心情，我们会去想如果吊着着的东西掉下来了或者起重机吊错了位置会发生什么样恐怖的情形。起重机的确是一种令人着迷的机械系统，无论是成人或者是孩子无不为止惊叹。起重机的种类五花八门，并且历史悠久。起重机是用一个或者几个简单的机器来组成一个机械结构并用于运送那些人无法搬动的物品。一般来说，起重机由一个卷筒、一束金属绳或是一条金属链组成来同时提升、放置成者足水平移动货物。起重机的.工作领域 一般处在需要装卸货物的运输业、需要搬运建材的建筑业和需要组装重型设备的制造业。1.概况第一台具有机械结构的起重机是由古希腊人发明的，并且由人或者牲畜比如驴，作为动力源。这种起重机被用于建筑的建造。这种起重机后来发展成了采用人力踏板驱动的更人性的起重机，用来提升更重 的物料。中世纪时港口起重机被叫来装卸船上的货物，有的港口起重机 为求更大的起重重量和更好的稳定性被造在了石塔里。最早的起重机是用木头制造的，工业革命之后，铸铁和钢材就代替了木头用于制造起重机。尽管水磨机和风车都可以利用自然的能源来驱动，但是几个世纪以来，起重机的动力源一直是人力或者畜力。第一台真正釆用机械能量的起重机用的是蒸汽机，最早的蒸汽起重机出现于18到19世纪，有一些甚至到了 20世纪末仍能很好地使用。虽然由于能源的供应仍不可及， 到现在有一些人力起重机还在使用，但是现代的起重机一般采用的内燃机、电动马达、液压系统能为起重机提供比之前大得多的提升力。2.历史2.1古希腊时期用来提升重型货物的起重机是希腊人在公元前六世纪晚期发明的。 考古记录显示最早在公元前515年提升夹具和铁制的吊楔开始出现在古希腊人石块结构的神殿里。由干这些是起重设备的核心装置、也由于他 们在石块的重心的中央或者趟在离重心上一点距离相等的两头被发现，他们被考古学家认为是起重机当时就存在的确凿证据。绞盘与滑轮的的引入导致了人类之前用斜坡来向高处运送货物的方法被广泛替代。在接下来的两百年中，希腊的建筑都采了这样新型的提升物料的技术，它利用了一些小型的石块来来代替人块的石头，这样更具实用性。与更早先的古希腊人神殿的建筑材料的尺寸不断变得越来越大趋势相比较，希腊古典庙宇比如帕台农神庙的石块重景都小于15- 20吨。而且，要把巨型的石柱竖立起来的作业使希腊人实际上更喜欢用好几块像鼓一样的圆柱石块堆叠而成。尽管确切何时从斜坡运输进入起重机提升技术时代的时间还不是很淸楚。但是当时古希腊不稳定的社会周势、和政治情况使得建造神殿更适合雇佣小观的、更加专业的建筑团队而不是像埃及和亚述那样大量使用的没有技术的分动力。这样的情况使得起重机更像希腊城邦发明 的而非釆用纯究动力斜坡运送货物的埃及或是亚述那样的独裁国家。文学上第一次的明确的记载滑轮组的复合系统是出现在亚里士多德的机械难题中，但清楚组成文字可能还要稍晚一些。与此同时，用于建造希腊神庙的石块尺寸再一次开始赶上他们的古代前辈了，这标志着当 时更多的久经考验的的滑轮组在希腊建筑史上找到了它们的一席之地。2.2古罗马时期起重机械在古代的全盛时期却足在古罗马帝国展幵的。当时建筑物的数景激增，而且这些建筑都达到了巨型的尺寸。罗马人采用了希腊人的起重机并将其发扬光大。多亏了那些维特兽程师们撰写的相当冗长 的文献和亚历山大帝的苍鹭的巢，我们才得以如此详细地了解到了它们的其中技术。三饼滑车是古罗马最简单的一种起重机，它是由一个单梁吊臂、一个 绞盘、一条绳子和一个三个滑轮组成的滑轮组组成的。经计算，假设一个人用尽力气能够长时间地提起相当于重 50千克的物体那么通过这样的起重机械他以提升约150千克的物体(3 个滑轮X50千克= 150千克）。更加重型的起重机就拥有五个滑轮（五饼 滑车），最大的起重机会在两根、三根甚至是四根桅杆上面装上三饼和 五饼的复合滑轮组（复滑车），这足由最大的负载载荷决定的。复滑车工作的时候两边需要4个人：两边各站两个已经可以提起重约3000千克的 物体（3条绳子X5个滑轮X4个人X50千克= 3000千克）。如果用踏车来代替绞盘的话，最大的起重载荷可以在人工减半的情况下达到两倍一 6000千克，因为踏车有更大的直径能够提供多个人的力矩。这意味着，和建造埃及金字塔时50个人才能通过斜坡搬动2.5吨的石块（50 千克每人）的情况相比，罗马的复滑车的提升能力把工作的效率提高60 倍（3000千克每人）。然而，大量现存的古罗马建筑中那些石块的重量比复滑车所能操作的负载耍重得多。这表明古罗马人全面的起重的能力要远远大于任何简单的起重机。以Baalbek的Jupiter神庙为例，那些楣梁的石块每块都重达60 吨以上，每个檐口的石块甚至达到了 100吨以上，所有这些石料都被提 升到了 19m的半空中。在罗马Trajan之柱的主要石块重达53. 3吨，而这些石块必须被提升到34m的高度。（见Trajian之柱）2.3中世纪时期在中世纪时，随着西罗马帝国的灭亡，欧洲的科技技术水平一落千丈。这时踏车式的起重机再次被大范围地使用。最早的提到踏车式是大约1225年法国的一部档案文学作品，它在一份手稿上也说明叙述了直到 1240年法国人的血统起源。在航海方面，最大的港口起重机是在1244 年的 Utrecht、1263 年的 Antwerp、1288 年的 Brugge 和 1291 年的 Hamburg, 而在英格兰踏车式的起重机直到1331年才有所记录。一般来说，釆用起重机来垂直运输比传统的方法更加的安全和经济。典型的应用领域就包括港口、矿井。值得一提的是在哥特式人教堂的建 造过程中，踏车式的起重机起到了一个不可成缺的重要作用。但是，档 案和图画都显示了当时新引进的机械系统如踏车、独轮手推车等却没有完全替代那些楼梯、木桶、手推车等依赖劳动力的生产方法。这样，旧式的和新式的机械在继续在中世纪的建筑和港口共存。除了踏车，中世纪的文献中也记载了由手动驱动带幅轮和曲柄的绞盘的起重机，在15 世纪时也是由卷扬机发展成为了类似船轮的系统。为了缓冲这些不规则的冲击力和解决提升过程中的死点问题，调速轮最早在1123年开始投入使用。踏车式起觅机具体以何种方式再次被釆用的已经无从考证，尽管它多次被使用在建筑领域，被毋庸置疑地认为和哥特式建筑的崛起有相当密切的关系。踏车式起重机的再次出现可能导致了卷扬机的技术发展，因 为卷扬机在踏车式起重机的结构和机械方面都有所发展。中世纪的踏车可以看作是罗马Vitruvius De 工程师设计品的一个精心改造品，它们可以在很多寺庙馆藏中看到。3.结构与用途中世纪的踏车结构是由一个木轮