梁桥

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中文1100字，英文1080个

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[来源：http://Doc163.com]

In designing a bridge, preference is often given to beam structure, unless it has a very long span. Simple in structure, convenient to fabricate and erect, easy to maintain, and with less construction time and low cost, beam structure has found wide application in bridgework. In 1937, over the Qiantang River, in the city of Hangzhou, was erected a railway-highway bi-purpose bridge, with a total length of 1453m, the longest span being 67m. When completed, it was a remarkable milestone of the beam bridges designed and built by Chinese engineers themselves before liberation. Since 1949, this kind of bridge has made giant strides. [资料来源：http://doc163.com]

Reinforced concrete beam structure is the most commonly used for short- and medium-span bridges. A representative masterpiece is the Rong Jiang Bridge completed in 1964 in the city of Nanning, the provincial capital of Guangxi Zhuangzu Autonomous Region. The bridge, with a main span of 55m and its cross section of a thin-walled box with continuous cells, was designed in accordance with closed thin-walled member theory, the first of its kind in China. [版权所有：http://DOC163.com]

梁桥构造简单、施工方便、工期短、造价低、且维修容易，除特大跨度桥梁外，是设计中优先考虑的结构体系，应用甚广。1949年前由国人设计监造的梁桥，以总长1453m，最大跨度67m的杭州钱塘江公路铁路两用桥（1937年建成）为一里程碑，1949年后这种梁桥已有长足的发展。 [版权所有：http://DOC163.com]

    钢筋混凝土梁桥是一种常用的中小跨度桥梁，以广西壮族自治区的南宁邕江桥（1964年）为代表，主跨最大55m，系中国最早按闭口薄壁构件设计的一座箱形悬臂梁桥。

    预应力混凝土梁桥在本世纪50年代中国即已开始研制，1956年初首先在陇海线新沂河铁路桥上建成了跨度23.9m的简支梁。跨度20m的京周公路桥也于同期建成。这种桥型的最大跨度为浙江省瑞安飞云江桥（跨度为62m，1988年）；1989年建成的开封黄河大桥总长4475.09m，其中有77孔50m简支梁采用连续长度达450m，并按部分预应力混凝土结构设计。
[资料来源：http://Doc163.com]