外文翻譯---混凝土梁橋的結構形式-文庫吧資料
2025-05-22 09:11本頁面
【正文】 in .and widths of 3 to 4 ft .For a standard highway HS20 loading, they are suitable for spans to about 50 ft, Standard channel sections are available in depths from 21 to 35 in a variety of widths, and are used for spans between about 20 and 60 ft .The hollow box beamsand singletee girders are intended for longer spans up to about 100 ft. For mediumspan highway bridges ,to about 120 ft ,AASHTO standard I beams are 4 generally used .They are intended for use with a posite castinplace roadway slab .Such girders often bine pretensioning of the precast member with posttensioning of the posite beam after the deck is placed .In an effort to obtain improved economy ,some states have adopted more refined designs ,such as the State of Washington standard girders. The specially designed precast girders may be used to carry a monorail transit system .The finished guide way of Walt Disney World Monorail features a series of segments, each consisting of six simply supported pretensioned beams ,together to from a continuous structure .Typical spans are 100 to 110 ft . Approximately half of the 337 beams used have some bination of vertical and horizontal curvatures and variable super elevation .All beams are hollow, a feature achieved by inserting a styrofoam void in the curved beams and by a moving mandrel in straight beam production. Precast girders may not be used for spans much in excess of 120 ft because of the problems of transporting and erecting large, heavy units. On the other hand ,there is a clear trend toward the use of longer spans for bridges .For elevated urban expressways ,long spans facil
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