摘要：随着高等级公路的迅速发展，中等跨径桥梁的数量大幅增加。桥面连续的简支梁结构体系由于存在桥面容易开裂等缺点在与连续梁结构体系的竞争中常常处于下风。但是现浇连续梁的施工复杂繁琐，费时费力，因此人们开始设想把两者的优越性结合起来来加快连续梁的建设速度，由此产生了先将整跨梁板预制，架设就位，后在端部浇注混凝土并张拉预应力钢束使之连续的先简支后连续施工方法。

 本次毕业设计的任务是下元大桥设计，旨在运用桥梁计算软件迈达斯设计计算一座5x30m先简支后连续的预应力混凝土连续箱梁桥的内力，并对其进行结构计算分析.首先根据毕设任务书要求和国家公路桥梁设计规范，拟定了三种桥型方案进行比选，最终选择5x30m预应力混凝土连续箱梁桥为本次的推荐设计桥型方案。然后用迈达斯软件建立5x30m预应力混凝土连续箱梁桥边梁及中梁的有限元模型并计算其在不同荷载组合下的内力，接着用迈达斯软件进行主梁截面的验算，最后，整理计算结果。并运用cad画出相应的施工设计图。

关键词：迈达斯软件；预应力混凝土连续梁桥；箱梁；先简支后连续施工方法

the Design of Xia Yuan Bridge

Abstract：With the rapid development of high-grsde highway, the number of bridges of middle-length increases substantially. Simply supported girder bridges with continuous decks are inferior to those of continuous girder bridges because their decks crack easily. 0wing to the complex construction of continuous girder bridges.which is time-consuming and laboursome, so people began to think about an approach to combine the advantages of the two so as to speed up the building of continuous girders. Thus the simply supported-continuous construction method, which is applied to erect full span girders. by the prefabrication technology first and then pour concrete in the end region of the girders and tension prestressed tendons to make them continuous, is introduced.

In this graduation design, my task is the design of Xia Yuan Bridg. The sobject aims to use large the bridge software——Midas to design and make the calculation of internal force and analysis the structure of a simply supported-continuous prestresed concrete continuous girder bridge with a length of 5x30 meters. First,according to the project requirements and the relevant provisions of the relevant national design regulations，three plans are proposed for comparison. After the selection of various kinds of bridge, the prestressed concrete continuous girder bridge with span of 5x30 is adopted to design the bridge plan.Next，the finite element model of side girder and middle girder of 5x30 meters prestressed concrete continuous box girderbridge was established and make the calculation of internal force under different load combinations by Midas software. And then,the characteristices of the girder cross-section are checked. Finally, make the calculations, and use CAD to make the mapping of drawings.

Keywords：Midas software；concrete continuous girder bridge；box girder；a simply supported-continuous prestresed concrete continuous construction method

目录

1绪论 1

1.1  预应力混凝土连续梁桥概述 1

1.2  毕业设计的目的与概述 3

1.2.1  毕业设计的目的 3

1.2.2  毕业设计概述 3

2设计资料 5

2.1  桥梁概况 5

2.2  设计参数 5

2.3  技术条件 5

2.4  设计要求 5

2.4.1 方案设计部分 5

2.4.2  结构设计部分 5

2.5  规范标准 6

3 桥跨总体布置及结构尺寸拟定 7

3.1  本桥主要材料 7

3.2  尺寸拟定 7

3.3  桥孔分跨 7

3.4  截面形式 8

3.4.1  立截面 8

3.4.2  横截面 9

3.5  梁高 9

3.6  细部尺寸 9