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关键词：设计 连续梁桥 先简支后连续 预应力
Abstract
The continuous beam bridge is a kind of bridge type used widely on the project. It not only has a reliable strength, stiffness and cracking, but also has a smooth journey comfortable, conservation work on the design and construction experience of the characteristics of maturity. Design a bridge must be laid across from the bridge-laying, the size of the development, steel beam layout and construction methods, but also give full consideration to the design parameters and environmental impact. This is a design for a three-span continuous bridge, whose cross-section is forms a single box with double chamber cast-in-situ box girder. The first design includes constant load, the live load and the calculation of the internal forces. On the basis of a load combination, we can draw moment and shear envelope map. Next, according to the short-term effect combination disposition prestressed reinforcement, and carries on the loss of prestress the computation. Finally, carries on the checking calculation to this continuous bridge, whether to satisfy the design requirements.
Continuous girder is supported on several piers. In the loading, different section girder on some positive, some negative bending moment, and the absolute value of the same span bridge beam small. So, can save the girder material dosage. Continuous beam bridge is usually 3 ~ 5 hole into a united, no deck joints in a, travel more suitable. Construction of continuous beam bridge, main girder erection can be by hole as simply supported beams are then connected to one another as a continuous beam. Or from the pier on the piecewise overhang extended finally connected into continuous beam. Nearly one, twenty years, in the construction of prestressed concrete continuous beam, successfully using the incremental launching construction, namely in the bridge end (or both) on the embankment piecewise continuous production of beam segmentally to span, the construction is more convenient. Continuous positive bending moment and negative bending beam bridge, construction is complex. In addition, the girder continuous beam bridge is a statically determinate structure, the uneven settlement will cause the change of beam hole internal force. Therefore, continuous beam foundation condition is better, generally used for large span bridges. Built in 1966, the United States of America in Astoria bridge, is currently the largest span continuous steel truss girder bridge, its span of 376 meters. Prestressed concrete continuous beam bridge in the development and application in China although only 20 years of history, but now in City Road, road and railway construction is widely used in. At present our country in terms of design, construction, prestressed materials and equipment has made great progress and achievements, but with the international advanced level there is still a certain gap. Today, we need to constantly sum up experience, draw a lesson, in design theory, design, materials and construction technology of prestressed continuous improvement, continuous development, innovation. We believe that through joint efforts, in twenty-first Century we will be able to design and construction of prestressed concrete beam bridges in China, the level to higher level.
Key Words: design; continuous bridge; after a first simply-supported; prestress
1绪论
1.1 预应力混凝土连续梁桥概述
预应力混凝土连续梁桥以结构受力性能好、变形小、伸缩缝少、行车平顺舒适、造型简洁美观、养护工程量小、抗震能力强等而成为最富有竞争力的主要桥型之一。本章简介其发展：
由于普通钢筋混凝土结构存在不少缺点：如过早地出现裂缝，使其不能有效地采用高强度材料，结构自重必然大，从而使其跨越能力差，并且使得材料利用率低。
为了解决这些问题，预应力混凝土结构应运而生，所谓预应力混凝土结构，就是在结构承担荷载之前，预先对混凝土施加压力。这样就可以抵消外荷载作用下混凝土产生的拉应力。自从预应力结构产生之后，很多普通钢筋混凝土结构被预应力结构所代替。