论文总字数：33890字

摘 要

薄壁空心桥墩适用于多种桥墩结构，其力学稳定性能一直受到广泛地关注，它与强度问题有着等同重要的意义。大跨度桥梁的桥墩往往使用高强材料，薄壁结构等，它的稳定问题更显得重要。如果处理不得当，结构可能出现整体失稳或是局部失稳。一般来说，薄壁空心桥墩的局部稳定主要是通过设置横隔板或者是控制壁厚来增强，而在规范中尚未有具体明确的规定。

本文以尕玛羊曲黄河特大桥为工程背景，其主桥上部为（65 5×120 65）m预应力混凝土连续刚构，下部主墩为单薄壁空心墩。首先对板的屈曲应力进行了研究，通过ANSYS有限元软件，对四边简支受压板特征值进行分析，得出屈曲应力，并与理论公式进行了对比。其次利用实体单元建立模型，通过进行特征值屈曲分析，得出其发生局部失稳的条件为宽厚比大于35，利用板的屈曲应力公式推导出薄壁空心墩发生局部屈曲时宽厚比需要满足的条件，对是否需要设置横隔板提出了建议。然后，分别用压杆单元和压板单元对不同宽厚比下的薄壁空心桥墩进行了稳定性问题的分析，对第一类失稳下的屈曲临界荷载以及第二类失稳下的极限承载力进行了比较分析。得出两类稳定下的临界荷载都是随着压杆宽厚比的增加而减小，第二类失稳临界荷载更贴近实际。桥墩的宽厚比对整个桥墩稳定性的影响起到决定性的作用。

桥墩的高度同样是影响桥墩稳定性能的因素之一，基于非线性有限元屈曲稳定分析，评估不同高度的桥墩在施工阶段以及成桥阶段的稳定性能，并分析了是否考虑钢筋作用对桥墩稳定性的影响。施工阶段不利工况下的两类稳定安全系数均大于运营状况时的两类稳定安全系数，说明施工阶段工况相比于运营工况较安全。考虑钢筋作用时，压杆的临界荷载提高了约30%。在考虑和不考虑钢筋作用的时候，两类稳定下的临界荷载都是随着高度的增加而减小。

关键词：薄壁空心桥墩；宽厚比；非线性分析；整体稳定；局部屈曲

Abstract

Thin-wall hollow pier is suitable for a variety of bridge structure; its mechanical stability has been widely attention. Stable performance and strength problems have the same significance. Large span bridge piers often use high strength material, thin-walled structure, etc., its stability problem is more important. If handled improperly, structural overall buckling or local buckling may occur. In general, the local stability of the thin-wall hollow pier is mainly controlled by setting the diaphragm plate and set the wall thickness, and there is no specific clearly defined in the specification.

The engineering background is based on the Gamayangqu Yellow River bridge, which the main bridge upper structure is (65 5 x 120 120) m prestressed concrete continuous rigid frame, the main piers is single thin-wall hollow pier. Firstly, ANSYS finite element software was used to study the plate buckling stress. Through the four edges simply supported linking piece eigenvalue analysis. It can conclude the buckling stress, and compared with the theoretical formulas. After using the entity unit model, it can conclude the local buckling condition, through the eigenvalue buckling analysis. It is concluded that the local buckling conditions happen when the wall slenderness ratio is greater than 35.Then, analyzed the stability problem of thin-wall hollow piers which have different thickness, by using compressive bar unit and compressive plate unit. In the end, it is compared the linear stability under the critical buckling load and the nonlinear stability under ultimate load of the piers. Two kinds of stability critical load were obtained reduced with the increase of wall slenderness ratio. The non-linear stability buckling critical load is closer to the actual. The wall slenderness ratio of the bridge piers plays an important role on the stability of the whole bridge pier.

The height of the bridge pier is also one of the factors affecting the stability of the bridge pier. Basing on nonlinear finite element buckling stability analysis, it was evaluated the stability of the different height of piers in the construction phase and the performance of phase, and analyzes bridge piers’ stability under the condition of considering the effect of the reinforcement or not. Two kinds of safety coefficient of construction stage adverse conditions are greater than two kinds of safety coefficient of the operating conditions. It can be explained that construction stage of project compared to the operation is safer. With the effect of the reinforcement, critical load of compressive bar will increase by about 30%. Two kinds of stability critical load are reduced with the increase of the height, in considering and not considering the effect of reinforcement.

Key words: thin-walled hollow pier; wall slenderness ratio; nonlinear analysis; the overall stability; local buckling

目录

第一章 绪论 1

1.1桥墩结构形式概述 1

1.2薄壁空心桥墩的发展及其在实际工程中应用 2

1.3研究稳定问题的必要性 4

1.4薄壁空心桥墩国内外研究现状 5

1.5 结构稳定理论概述 6

1.5.1两类稳定问题 6

1.5.2平衡分岔失稳的求解方法 7

1.6 工程概况 8

1.7本文工作 10

第二章 矩形截面空心墩的弹性屈曲理论分析 11

2.1概述 11

2.2四边简支受压板屈曲特征值理论解 11

2.3有限元分析与理论解的对比 16

2.4本章小节 18

第三章 宽厚比对薄壁空心桥墩稳定性的影响 19

3.1概述 19

3.2极限承载力的求解 19

3.3桥墩稳定问题分析 22

3.3.1压杆单元模拟 23

3.3.2压板单元模拟 24

3.3.3两类理论下的有限元分析结果对比 25

3.4本章小节 26

第四章 桥墩高度对薄壁空心桥墩稳定性的影响 27

4.1概述 27

4.1.1研究方法 27

4.1.2第一类失稳荷载的求解 27

4.1.3第二类失稳荷载的求解 28

4.2两种工况下的荷载 30

4.2.1施工阶段 30

4.2.2运营状态 30

4．3不考虑钢筋作用下极限承载力的求解 31

4.3.1施工阶段受力下的两类失稳分析 31

4.3.2运营状况受力下的两类失稳分析 31

4.3.3两种工况下的对比分析 31

4．4考虑钢筋作用下极限承载力的求解 33

4.4.1钢筋对桥墩稳定性的影响 33

4.4.2施工阶段受力下的两类失稳分析 34

4.4.3运营状况受力下的两类失稳分析 34

4.4.4两种工况下的对比分析 35

4.5是否考虑钢筋对两类稳定的影响 36

4.6本章小节 37

第五章 结论与展望 39

5.1全文总结 39

5.2展望 39

致谢 41

参考文献 42

第一章 绪论

随着国内高速交通建设的迅速发展，越来越多的大跨度混凝土桥梁正在修建中，综合考虑设计车速大、跨越深沟峡谷、环境保护等因素，高架桥的出现极大促进了空心桥墩的发展与应用。超过40米的高墩比比皆是，甚至越来越多的100米以上的高墩已经建成或者正在修建。正是因为空心截面在高墩中具有减少自重、减少地震力、减少圬工等优秀特性使得它被越来越多地被采用。这其中，在世界范围内的欧洲、美国和中国尤其多。

1.1桥墩结构形式概述

根据桥墩的构造大体可以分成以下几类：

1.1.1实体桥墩

剩余内容已隐藏，请支付后下载全文，论文总字数：33890字