【導(dǎo)讀】交流和鞏固國防等方面，都具有非常重要的作用。在鐵路，公路，城市和農(nóng)村道路交。中，橋梁不僅在工程規(guī)模上十分巨大，而且也往往是保證全線早日通車的關(guān)鍵。尤其是箱型簡支梁的應(yīng)用，箱形簡支梁橋主要用于預(yù)應(yīng)力混凝土梁橋。于橋面較寬的預(yù)應(yīng)力混凝土橋梁結(jié)構(gòu)和跨度較大的斜交橋和彎橋。本課題研究了跨徑為30m的預(yù)應(yīng)力混凝土箱型簡支梁橋。解決了全橋各部結(jié)構(gòu)。制全橋施工設(shè)計圖。制全橋施工技術(shù)設(shè)計圖時應(yīng)用了計算機輔助制圖。了大量鋼材，符合我國可持續(xù)發(fā)展道路。新中國成立以來，我國的板橋建設(shè)取得了巨。大的成就，充分體現(xiàn)了設(shè)計者和勞動人民的勤奮和智慧。然而，面臨著瞬息萬變的世。受力要求外，還要考慮布置預(yù)應(yīng)力鋼束到的需要，擬定高度為30cm，其余部分為20cm，近梁端處腹板厚度考慮布置預(yù)應(yīng)力鋼束到的需要和抗剪墻厚度的要求，定為30cm，傳遞，避免在轉(zhuǎn)角處產(chǎn)生過大的應(yīng)力集中。梁端部分區(qū)段由于錨

　　

【正文】 en deaths were caused by the bends. When extra strength is necessary in the piers, they are sometimes keyed into the bedecksthat is, that are extended down into the bedrock. This method was used to build the piers for he Golden Gate Bridge in San Francisco, which is subject to strong tides and high winds, and is located in an earthquake zone. The drilling was carried out under water by deepsea divers. Where bedrock cannot be reached, piles are driven into the water bed. Today, the piles in construction are usually made of priestesses concrete beams. One ingenious technique, used for the Tappan Zee Bridge across the Hudson River in New 畢業(yè)設(shè)計 33 York, is to rest a hollow concrete box on top of a layer of piles. When the box is pumped dry, it bees buoyant enough to support large proportions of the weight of the bright of the bridge. Each type of bridge, indeed each individual bridge, presents special construction problem. With some truss bridge, the span is floated into position after the piers have been erected and then raised into place by means of jacks or crams. Arch bridges can de constructed over a false work, or temporary scaffolding. This method is usually employed with reinforced concrete arch bridges. With steel arches however, a technique has been developed where by the finished sections are held in place by wires that supply a cantilever support. Cranes move along the tension in the cables increases. With suspension bridges, the foundations and the towers are built first. The foundation and the towers are built first. Then a cable is run form the anchorage concrete block in which the cable is fastenedup to the tower and across to the opposite tower and anchorage. A wheel that unwinds wire from a reel runs this cable. When the reel reaches the other side, anther wire is placed on it, and the wheel returns to its original position. When all the wires have been put in place, another machine moves along the cable to pact and to bind them. Construction begins on the deck when the cables are in place, with work progressing toward the middle from each end of the structure. Bridge design is probably the hardest brain work in civil engineering. Bridge designers have a long period of training, only the best of them succeed, and only a small fraction of the bridge they design are built. The time from the first proposal for a bridge to the provision of the money for its construction is usually 畢業(yè)設(shè)計 34 long and many bridges have been built only after the beat of their designer. A fine bridge engineer, shirley smith, who was the contactor agent for the Forth Road Bridge, has written very well about his love of bridge work in his book Great Bridges of the World. For those who work on the site, bridge is hard in other way. They cannot settle down in one house because they rarely work in one place for longer than a year or two, and the working site is usually unprotected and something dangerous. The builders of the Forth Road Bridge〈 1965〉 were particularly proud of the fact no lives were lost in spite of the heavy winds, the snow and the cold rain. Work on bridge foundations, usually in cofferdams and something in caissons under pressed air has often caused loss of life. One of the most interesting recent bridges, which will remain for many years the world′ largest, if not its longest, is the VarianNarrows Bridge, New York, pleted in 1964, a suspension bridge of 4,260ft main span, having six traffic lanes on each of its two deck. It is also probably one of the world’s highest bridges since its main span has to be 216ft above the shipping channel which is 2,00ft wide. Its capacity is estimated at 13 million vehicles in the first year, rising eventually to 48 million vehicles, and it cost some 324million dollars to build. The main parts of a suspension bridge are the deck, the two cables and many suspenders transferring the deck load to the cables, the towers over which the cables passed the anchorages on the two banks. The Narrows Bridge has four cables, two on each side. In a selfanchored suspension bridge there are no anchorages, the two ends of the cables being tied to the shore ends of the bridge structure. Most road bridges have pies rising out of the 畢業(yè)設(shè)計 35 valley, on which the girders rest, with a deck carried by the girders and a wearing surface on top of the deck. Railway bridges sometimes differ in the wearing surface being unnecessary and therefore left out pletely, so that wearing surface being unnecessary and therefore left out pletely. The clear span of a bridge is the gap from the near edge of one pier to the near edge of the next. The effective span is the spacing between the centre of bridge piers. The span, which is large than the clear span, is used in the design of the girders. At each shore, every bridge has foundation called abutments, an abutment being a foundation which carries horizontal load. An interesting and economical bridge which has bee popular in Europe in the last twenty years and was first used in Germany is called the cable cantilever or bridle chord bridge, though other names have been used for it. The simplest type of span is a beam bridge, consisting of a rigid beam between two supports. Today most simple beam bridges are strengthened by a truss, which is based on the triangle. Diagonal bans that extend between the horizontal and vertical beams give support against both pression and tension. Many early truss bridges were built of wood。 one that was erected across the Susquehanna River in Pennsylvania in 1815 had a span of 110 meters. Iron and then steel were later used in the construction of truss bridges, still further increasing their strength. Trusses are not only strong but also light, because all unnecessary material has been eliminated in their design. Another type of beam bridge is the cantilever,