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一、概 述 上承式吊桥是七十年代国外出现的一种新型结构。这种桥型,适宜于在深谷陡坡地带,且桥下净空不受限制的条件下修建。1972年5月在哥斯达黎加建成了世界上第一座这样的预应力混凝土吊桥——里奥·科洛拉多(Rio Colorado)桥,主跨跨长为124米,从而为预应力混凝土桥梁开辟了一个新的领域。以后,日本在1977年又建成了这样的一座,跨长为54米,成为世界上的第二座。从国外已建成的这两座桥梁来看,它们与原来的下承式吊桥相比,有着许多显著的特点,这可通过图1中两者的对比来说明:
First, an overview of the overhang suspension bridge is a new type of structure appeared in the seventies abroad. This type of bridge is suitable for construction on steep slopes of deep valleys with unlimited headroom under the bridge. The first such prestressed concrete suspension bridge in the world, the Rio Colorado bridge, was completed in Costa Rica in May 1972 with a main span of 124 meters spanning the prestressed concrete bridge A new area. Later, in 1977, Japan built another such landmark, with a span of 54 meters, making it the second largest in the world. Judging from the two completed bridges abroad, they have many notable features compared with the original underfloor suspension bridges, as illustrated by the contrast between the two in Figure 1: