摘 要

大跨径预应力混凝土连续刚构桥有跨越能力大、结构刚度好、行车平顺、养护简单、抗震性能好等优点，广泛应用在桥梁建设领域。收缩徐变是混凝土本身特有的性质，对大跨径预应力混凝土连续刚构桥有着显著的影响，会影响悬臂施工的合拢质量和引起桥梁长期运营跨中下挠。因此，正确地预测收缩徐变效应对大跨径预应力混凝土连续刚构桥变形和应力的影响,具有重要的理论和实际工程意义。

本文在广泛收集和阅读国内外混凝土收缩徐变效应研究资料的基础上,对混凝土的收缩徐变的机理和影响因素、收缩徐变的几种常用的预测模型进行总结。以湖北恩施石板溪大桥为工程背景，运用桥梁专业有限元分析软件Midas/Civil建立全桥有限元模型，对施工阶段及运营阶段进行收缩徐变计算分析，通过计算得到石板溪大桥主梁成桥后不同时期的应力和变形，分析收缩徐变效应对大跨径预应力混凝土连续钢构箱梁桥的影响。主要研究内容有以下几部分：

1. 以石板溪大桥(65 120×2 65m)预应力连续刚构桥为工程背景，运用桥梁专业有限元分析软件Midas/Civil建立全桥有限元模型，进行有限元仿真分析。

（2）研究混凝土收缩徐变对连续刚构桥运营10年内应力分析，得到以下结论：对于主梁上缘，随着时间的推移，每个截面的应力值都增大，且各个时期应力最大值都在中跨合拢段及附近截面。在成桥刚开始初期，应力值变化较大。随着时间的推移，应力值的变化越来越小，最后趋于稳定。对于主梁上缘，成桥后前3年应力值约占10年内的78％；对于主梁下缘，前3年的应力值约占10年内的79％。而且前3年无论主梁上缘下缘，应力值变化都较大，3-10年应力值变化较小但仍在增长。

（3）进行变形分析，得到如下结论：收缩徐变对石板溪大桥连续箱梁的挠度影响很大，且对边中跨的影响明显大于边跨和中跨。成桥不同时期最大挠度值都在中跨合拢段及附近截面。对于整个主梁，前三年的挠度最大值约占成桥10年挠度最大值的71％，成桥3年内的收缩徐变引起的竖向挠度增长比较快，3到10年内变形增长比较缓慢，但仍在增长。

（4）对桥墩进行参数敏感性分析，分析不同桥墩高度下由收缩徐变引起的挠度变化。证明：桥墩不对称导致引起结构刚度不同，从而对收缩徐变结构产生影响，导致桥梁变形不对称。

关键词：连续刚构箱梁桥;有限元模型;收缩徐变;

Abstract

The long span prestressed concrete continuous rigid frame bridge has the advantages of good spanning capacity, no expansion joint of continuous beam, smooth running, low maintenance cost, good seismic performance, and so on. Shrinkage and creep is concrete itself unique nature, of long span prestressed concrete continuous rigid frame bridge has a significant impact, fold quality of the influence of the cantilever construction and cause long-term operation of bridge deflection in the mid span. Therefore, correctly predicting the effect of shrinkage and creep on the deformation and stress of long span prestressed concrete continuous rigid frame bridge is of great theoretical and practical significance.

Based on the widely collecting and reading at home and abroad in the effects of shrinkage and creep of concrete research, the mechanism and influencing factors of creep and shrinkage of concrete, shrinkage and creep of several common forecasting models were summarized in this paper. In Enshi, Hubei slate Creek Bridge as the engineering background, using bridge professional finite element analysis software MIDAS/civil to establish the finite element model of the bridge, on the construction stage and operation stage of shrinkage and creep analysis, obtained by calculating the slate Creek bridge girder to bridge after different periods of stress and deformation analysis of shrinkage and creep effect of long span prestressed concrete continuous steel box girder bridge effect. The main research results are as follows:

(1)With the（65 120 * 2 65）m prestressed continuous rigid frame bridge as the engineering background, the finite element model of the whole bridge was established by the finite element analysis software Midas/Civil , and the finite element simulation analysis was carried out.

(2)Study of concrete shrinkage and creep of continuous rigid frame bridge operation of 10 years of structural deformation analysis, get the following conclusion: for the upper edge of the beam, with the passage of time, each section of the stress values are increased, and various periods of stress maximum in the middle span closure segment and nearby section. In the initial stage of the bridge, the stress value is changed greatly. With the passage of time, the change of stress value is getting smaller and smaller, and finally tends to be stable. For the upper edge of the main girder, the stress value of the first 3 years after the bridge is about 10 in 78% years. For the lower edge of the main girder, the stress value of the first 3 years is about 79% in 10 years. And in the first 3 years, regardless of the upper edge of the main girder, the stress value changes are larger, the stress value of 3-10 is smaller but still growing.

(3)Deformation analysis, the following conclusions: the shrinkage and creep of the slab bridge continuous box girder deflection effect is great, and the impact on the edge of the cross is significantly greater than the cross and cross. The bridge in different periods of maximum deflection value of span closure segment in and near section. For the main girder, three years ago the deflection maximum accounted for about a bridge 10 years maximum deflection value of 71%, completion within three years of vertical deflection caused by creep and shrinkage is growing relatively fast, within 3 to 10 years, deformation is relatively slow growth, but is still on the rise.

（4）The sensitivity analysis of the parameters of the bridge piers is carried out, and the variation of the deflection caused by shrinkage and creep is analyzed. The results show that the bridge pier asymmetry leads to different structure stiffness, which influences the shrinkage and creep structure, which leads to the asymmetry of bridge deformation.

Key Words :Continuous rigid-frame box girder bridge;finite element;shrinkage and creep;

目 录

摘 要 I

Abstract II

第一章 绪论 1

1.1引言 1

1.2研究历史和现状 3

1.3本论文的研究背景和意义 4

1.4本论文的研究的主要内容 5

第二章 混凝土的收缩徐变 6

2.1 混凝土的收缩徐变的概念和特性 6

2.1.1混凝土的收缩 6

2.1.2混凝土的徐变 7

2.2 混凝土收缩徐变的机理 8

2.2.1混凝土收缩的机理 8

2.2.2混凝土徐变的机理 9

2.3 影响混凝土收缩徐变的因素 9

2.4收缩徐变对结构性能的影响 10

2.4.1内力重分布 10

2.4.2对结构变形的影响 11

2.5 混凝土徐变预测模型 11

2.5.1 徐变系数 11

2.5.2几种常用的徐变预测模式 12

2.6 混凝土收缩应变的预测模式 16

2.7施工中应注意的问题 17

第三章 工程概况与建模过程 18

3.1工程概况 18

3.1.1技术标准及技术规范 18

3.1.2基本设计资料 19

3.1.3 结构布置 20

3.1.4主要材料 20

3.1.5桥梁结构设计要点 21

3.2 建模过程 21