西南交大路桥毕业设计

西南交通大学桥梁毕业设计

62+104+104+62m预应力混凝土连续梁桥设计

摘要

本毕业设计主要是关于大跨度预应力混凝土连续梁桥上部结构的设计。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、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。受时间和个人能力的限制，本次毕业设计没有具体涉及到下部结构、横向预应力及竖向预应力的设计。

设计桥梁跨度为62m+104m+104m+62m,分为两幅设计，单幅为单箱单室，桥面总宽25m，双向4车道，上下行。主梁施工采用悬臂挂篮施工，对称平衡浇筑混凝土。施工分为21个阶段：第一阶段：施工临时支座并固结，浇筑墩顶0#段及边跨直线段满堂支架施工；第二阶段至第十七阶段：悬臂对称平衡浇筑混凝土至最大悬臂端；第十八阶段：边跨合拢；第十九阶段：中跨合拢,拆除挂篮设施，加载二期恒载；第二十施工阶段：预留施工阶段；第二十一阶段：运营阶段。本桥设5个支座，其中第3个支座为固定铰接支座，其余均为活动铰接支座。本设计中总共有9个临时支座。

设计过程如下：

首先，确定主梁主要构造及细部尺寸，它必须与桥梁的规定和施工保持一致，考虑到抗弯刚度及抗扭刚度的影响，设计采用箱形梁。主梁的高度呈二次抛物线变化，因为二次抛物线近似于连续梁桥弯距的变化曲线。墩顶截面通过腹板、底板的加厚以及设置横隔梁强度得以加强，底板厚度呈二次抛物线变化，底板厚度为0.7变为0.3。腹板厚度呈直线变化，由0.75变为0.4。顶板厚度沿全桥保持不变,均为0.28m。

其次，利用BSAS电算软件分析内力结构总的内力(包括恒载和活载的内力计算)。用于计算的内力组合结果也由BSAS电算软件计算而得，从而估算出纵向预应力筋的数目，然后再布置预应力钢丝束。

再次，计算预应力损失及次内力，次内力包括先期恒载徐变次内力、先期预应力徐变次内力、后期合拢预应力索产生的弹性次内力、局部温度变化次内力。

然后进一步进行截面强度的验算，其中包括承载能力极限状态和正常使用极限状态。在正常使用极限状态验算中包括计算截面的混凝土法向应力验算、预应力钢筋中的拉应力验算、截面的主应力计算。

关键词：预应力混凝土连续梁桥、次内力、悬臂施工

Abstract

The graduate design is mainly about the design of superstructure of long-span pre-stressed concrete continuous box Girder Bridge . Pre-stressed concrete continuous Girder Bridge become one of main bridge types of the most full of competion ability because of subjecting to the dint function with the structure good, having the small defomation,few of control joint,going smoothly comfort,protected the amout of engineering small and having the powerfully ability of earthquake proof and so on. For time and ability limited, the design of the substructure, transverse pre-stressing and vertical pre-stressing is not considered.

The spans of the bridge are 62m+104m+104m+66m,main beam is respective designed, each suit has one box one room and four traffic ways of all, the width of the bridge surface is 25m.

The major girder applies cantilever hung-basket bearing, symmetric equilibrium construction .There are twenty-one steps in the working. The 0# member is worked in the first step , then form the second step to the seventeenth the other members is worked before they are jointed except the ones are siuated in the beside or middle of span and the substructure is

worked in the steps; and then it’s jointed in the site of beside spans in the eighteenth step; and then mid-span is jointed in ninteenth step; and remove the hung-basket bearing then the second dead loads is in effect in the step; the tweentith stage: vacant construction stage; in the last step, the structure is running. There are five bearings, the third is fixed bearing, the left four are expansion bearings. In the design there are nine casual bearing.

The procedure of the design is listed below:

The first step as to dimension the structural elements and details of which it is composed, it can’t and certainly should without being fully coordinated with the planning and working phrases of the project. Considering the distorting stiffness and the bending stiffness, box birder goes as second-parabolic curve, for second-parabolic curve is generally similar to the change of continuou s bridge’s bending moments along. The sectionat the support is strengthened by the provision of thickened webs , bottom slabs and a cross beam , the thickness of the bottom slab is changed in second-parabolic curve and the thickness of the web is changed in linearity, the former varies from 0.7m to 0.3m, the latter varies from 0.75m to 0.4m, the top slab’s thickness is 0.28m.

The second step is to use BSAS software to analyze internal gross force of the structures(including dead load and lived load), the internal force composition can be done by using the compute results. According to the internal force composited, the evaluated amount of longitudinal tendons can be worked out, then we can distribute the tendons to the bridge.

The third steps is to calculate the loss of pre-stressing and secondary force due to pre-stressing, first dead loads and temperature, bearing displacement, and so on.

The last steps is checking the main cross section. the work includes the load-caring capacity ultimate state and the nor mal service ability ultimate state as well as the main section’s being out of shape.

Key Words: Pre-stressed concrete continuous girder bridge, Secondary force，Cantilever constructed

目录

第1章绪论 1

1.1预应力混凝土连续梁桥概述 1

1.2 毕业设计的目的与意义 3

第2章桥跨总体布置及结构尺寸拟定 4

2.1 尺寸拟定 4

2.1.1 桥孔分跨 4

2.1.2 截面形式 4

2.1.3 梁高 5

2.1.4 细部尺寸 6

2.2 主梁分段与施工阶段的划分 7

2.2.1 分段原则 7

2.2.2 具体分段 7

2.2.3 主梁施工方法及注意事项 7

第3章荷载内力计算 9

3.1 恒载内力计算 9

3.2 活载内力计算 11