橋梁專業(yè)畢設(shè)文獻(xiàn)翻譯(參考版)
2024-11-06 04:23本頁面
【正文】 3.) Cable arrangements also vary greatly. Some typical varieties are mono, harp, fan, and star arrangements (illustration 4.) In some cases, only the cables on one side of the tower are attached to the girder, the other side being anchored to a foundation or other counterweight. Suspension Of all the bridge types in use today, the suspension bridge allows for the longest spans. At first glance the suspension and cablestayed bridges may look similar, but they are quite different. Though suspension bridges are leading long span technology today, they are in fact a very old form of bridge. Some primitive examples of suspension bridges use vines and ropes for cables. The development of metals brought the use of linked iron bars and chains. But it was the introduction of steel wire ropes that allowed spans of over 500m to bee a reality. Today the Akashi Kaikyo bridge boasts the world39。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 girder and truss bridges, both ends of an arch are fixed in the horizontal direction (. no horizontal movement is allowed in the bearing). Thus when a load is placed on the bridge (. a car passes over it) horizontal forces occur in the bearings of the arch. These horizontal forces are unique to the arch and as a result arches can only be used where the ground or foundation is solid and stable Like the truss, the roadway may pass over (illustration 1) or through an arch (illustration 4) or in some cases both (illustration 3.) Structurally there are four basic arch types: hingeless, twohinged, three hinged and tied arches. The hingeless arch (illustration 1) uses no hinges and allows no rotation at the foundations. As a result a great deal of force is generated at the foundation (horizontal, vertical, and bending forces) and the hingeless arch can only be built where the ground is very stable. However, the hingeless arch is a very stiff structure and suffers less deflection than other arches. The two hinged arch (illustration 2) uses hinged bearings which allow rotation. The only forces generated at the bearings are horizontal and vertical forces. This is perhaps the most monly used variation for steel arches and is generally a very economical design. The threehinged arch (illustration 3) adds an additional hinge at the top or crown of the arch. The threehinged arch suffers very little if there is movement in either foundation (due to earthquakes, sinking, etc.) However, the threehinged arch experiences much more deflection and the hinges are plex and can be difficult to fabricate. The threehinged arch is rarely used anymore. The tied arch (illustration 4) is a variation on the arch which allows construction even if the ground is not solid enough to deal with the horizontal forces. Rather than relying on the foundation to restrain the horizontal forces, the girder itself ties both ends of the arch together, thus the name tied arch. Cable Stayed A typical cable stayed bridge (illustration 1 amp。t attempt that here. A box girder is much the same as an Ibeam girder except that, obviously, it takes the shape of a box. The typical box girder has two webs and two flanges (illustration 2.) However, in some cases there are more than two webs, creating a multiple chamber box girder. Other examples of simple girders include pi girders, named for their likeness to the mathematical sy
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