桥梁专业毕设文献翻译

桥梁专业毕设文献翻译内容摘要：

and continuous trusses. The small size of individual parts of a truss make it the ideal bridge for places where large parts or sections cannot be shipped or where large cranes and heavy equipment cannot be used during erection. Because the truss is a hollow skeletal structure, the roadway may pass over (illustration 2) or even through (illustration 1) the structure allowing for clearance below the bridge often not possible with other bridge types. Trusses are also classified by the basic design used. The most representative trusses are the Warren truss, the Pratt truss, and the Howe truss. The Warren truss is perhaps the most mon truss for both simple and continuous trusses. For smaller spans, no vertical members are used lending the structure a simple look (illustration 1.) For longer spans vertical members are added providing extra strength (illustration 2.) Warren trusses are typically used in spans of between 50100m. The Pratt truss (illustration 3) is identified by its diagonal members which, except for the very end ones, all slant down and in toward the center of the span. Except for those diagonal members near the center, all the diagonal members are subject to tension forces only while the shorter vertical members handle the pressive forces. This allows for thinner diagonal members resulting in a more economic design. The Howe truss (illustration 4) is the opposite of the Pratt truss. The diagonal members face in the opposite direction and handle pressive forces. This makes it very uneconomic design for steel bridges and its use is rarely seen. Rigid Frame Rigid frame bridges are sometimes also known as Rahmen bridges. In a standard girder bridge, the girder and the piers are separate structures. However, a rigid frame bridge is one in which the piers and girder are one solid structure. The cross sections of the beams in a rigid frame bridge are usually I shaped or box shaped. Design calculations for rigid frame bridges are more difficult than those of simple girder bridges. The junction of the pier and the girder can be difficult to fabricate and requires accuracy and attention to detail. Though there are many possible shapes, the styles used almost exclusively these days are the pishaped frame, the batter post frame, and the V shaped frame. The batter post rigid frame bridge is particularly well suited for river and valley crossings because piers tilted at an angle can straddle the crossing more effectively without requiring the construction of foundations in the middle of the river or piers in deep parts of a valley (illustration 1). V shaped frames make effective use of foundations. Each Vshaped pier provides two supports to the girder, reducing the number of foundations and creating a less cluttered profile (illustration 3.) Pi shaped rigid frame structures are used frequently as the piers and supports for inner city highways. The frame supports the raised highway and at the same time allows traffic to run directly under the bridge (illustration 2.) Arch After girders, arches are the second oldest bridge type and a classic structure. Unlike simple girder bridges, arches are well suited to the use of stone. Many ancient and well know examples of stone arches still stand to this day. Arches are good choices for crossing valleys and rivers since the arch doesn39。 t require piers in the center. Arches can be one of the more beautiful bridge types. Arches use a curved structure which provides a high resistance to bending forces. Unlike。