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桁架拱桥是继双曲拱桥之后发展起来的一种轻型拱桥。这种桥型结构轻巧,整体性强,对地基变形有一定的适应能力,在软土地基上、小跨径桥梁的建设中得到了广泛应用,并取得了较成熟的设计和施工经验。但是,随着桁架拱桥跨径的增大,墩台的增高,桥身自重和水平推力也随之增大,软土地基上桁架拱桥因墩台设计不当而发生事故的机率也越来越高。以“桁架拱桥之乡”的上海市金山县为例,1982年前在紫石泾建造的三座60m跨径桁架拱桥,都不同程度地出现了桥台沉降和位移,其中位移最大值达15cm,导致上部结构的变形和裂缝开展。1981年在朱泾镇建造的跨越秀州塘的万安桥,是金山县最大的公路桁架拱桥,因墩台设计不周,竣工不久即停止了使用。
Truss arch bridge is a light arch bridge developed after the double curved arch bridge. This kind of bridge structure is light, the whole is strong, and it has some adaptability to the foundation deformation. It has been widely used in the construction of small span bridges on soft soil foundation and has obtained more mature design and construction experience. However, with the increase of the cross-span of truss arch bridge, the increase of piers and abutments, the self-weight of bridge and horizontal thrust also increase, and the probability of accidents of truss arch bridges on soft soil foundation due to improper design of piers is also higher . Taking Jinshan County in Shanghai as an example, the three 60m span truss arch bridges constructed in Zishiqiao before 1982 all showed abutment settlement and displacement to varying extents. The maximum displacement Up to 15cm, leading to the deformation of the superstructure and crack development. Wan’an Bridge spanning Xiuzhou Tang in Zhujing Town in 1981 was the largest highway truss arch bridge in Jinshan County. Due to the poorly designed pier, it was stopped shortly after its completion.