摘    要

设计为总长为245m的公路直线预应力混凝土连续刚构桥,跨径组成为65m+115m+65m，截面形式为单箱单室箱型，墩身为双薄壁柔性墩。设计荷载标准为公路I级汽车荷载。主梁采用挂篮悬臂对称施工。因时间所限，未涉及下部结构（桥墩和基础）、横向预应力及竖向预应力的设计。

根据活载位置的不同，连续刚构桥的断面可能出现正弯矩或负弯矩，因而，要按弯矩变化的幅值布置预应力钢筋。连续刚构桥将连续梁与薄壁墩（柔性）固结而成，既保持了连续梁桥的优点，同时又节省了支座，减少墩与基础的工程量，并改善了结构的水平荷载作用下的受力性能，即各柔性墩按刚度比分配水平力。

参考了大量的工程实例，对结构方面进行了较为详细的分析和研究。横截面采用单箱单室截面，梁高按二次抛物线变化，从支座处最大5.8米到跨中2.5米，顶板厚度为25cm。为了减小施工难度，并结合连续刚构桥的受力特点，底板厚度呈直线线性变化，由支座向跨中减，支座处为0.7m,跨中为0.4m。运用BSAS对结构进行了内力分析,然后对钢筋数量进行估计并配置钢筋，检算主要控制截面的承载能力。绘制结构施工图，包括桥跨布置图、施工程序图等，进行外文翻译，最后编制设计计算说明书及文档整理。

【关键词】: 预应力混凝土连续刚构桥；悬臂施工；内力分析；

预应力损失；次内力。

Abstract

Design is a prestressing concrete continuing steel bridge, with the total length of 245m of the highway，spans are 65m, 115m, and 65m respectively, the form of the section is single-box single-room，and the piers are flexible double think-wall。 The standard of the loads is highway one car loads. The main beam of the bridge is constructed symmetrically by Hanging Basket cantilever。 Because of the time constraint, the design doesn’t contain the lower structure (piers and foundations), horizontal prestressing and vertical prestressing. According to the different position of the live loads, the section of this continuing steel bridge may have positive  structural forces and negative  structural forces，therefore, the arrangement of the prestressing reinforcement should vary in accordance with the change of structural forces. The continuing steel bridge is a combination of continuing beam and double think-wall piers (flexible), and it also changes the structure’s stress compatibility under the level of loads.

      Design is made on the basis of lots of real projects case, so it gives a detailed analysis and study of the structure. The  cross section is in form of  single-box single-room , the height of the beam changes according to the cross-section parabolic ，from the supports the maximal height is 5.8m to  the inter - Main beamheight of 2.5m, and the thick of the Roof is 22cm. In order to alleviate the difficulties of construction, the thick of the bottom ,combined with the stress feature of continuing steel bridge, changes in linear, reducing from the supports to the  inter - Main beam, the thick of the supports is 0.7m and the inter - Main beam is 0.4m. Upon the basis of the section design, making an analysis of internal forces of the structure by BSAS， evaluate the amounts of the reinforcement and arrange them accordingly, then check the capability of the main controlling section. Drawingthe structural construction plan, including the arrangement plan of the bridge span, the procedure of construction, etc. then translate them into English ,finally make the design illustration and Microsoft Word.

Key words: prestressing concrete continuing steel bridge;   cantilever construction;    analysis of internal forces;     prestressing lose;    secondary internal forces