摘 要

我国有很多在役钢桁架桥梁的使用寿命已经超过了50年，随着道路交通荷载的不断增加，使得桥梁桁架结构内部的疲劳损伤加快。这些钢桁架桥梁极易发生杆件疲劳破坏，并且杆件的疲劳破坏通常导致桥梁结构的断裂倒塌，这种断裂破坏具有突发性。为了保证桥体在通行时的安全性，需要通过有效方法对钢桁架结构进行疲劳验算从而推算出桥梁的剩余使用寿命。

本文首先采用ANSYS有限元分析软件进行钢桁架结构建模，根据相关钢桁架桥书籍资料采用桁架结构类型：合理跨径、节间长度、桁架高度、连接方式以及确定桁架杆件材料和截面特性。然后依次添加二期恒载和公路一级荷载中车道荷载的均布荷载，运用ANSYS软件模拟运行得出各类杆件中各自最大受力杆件。在各类的最大受力杆件相对应的桥面支点上继续添加车道荷载的集中荷载进行ANSYS软件模拟运行得出各类杆件最终受力大小，计算结果与杆件材料设计强度比较得出杆件在荷载作用下的强度可靠性。最后去掉所有恒载，保留车道荷载的均布荷载和集中荷载进行ANSYS软件模拟运行得出应力幅。通过应力幅绘制S-N曲线，运用S-N疲劳曲线法进行桥梁寿命计算，以及运用断裂力学方法和可靠度方法进行桥梁寿命评估，最终综合得出最优方案。

通过有效的分析计算表明，本文运用ANSYS有限元软件建立的仿真模型是可靠的。各项桥梁结构计算参数的选用都较为合理，结构荷载等因素需要考得虑全面，软件仿真的分析效果良好。S-N疲劳曲线法在预测钢桁架桥寿命上更易于操作计算，具有较高的精度和较广的运用前景。

关键词：钢桁架桥；ANSYS建模分析；钢桥疲劳问题；寿命评估

Abstract：

A lot of running time of the steel truss Bridges in service in our country more than 50 years, the increase of traffic load, accelerated the fatigue damage of bridge truss structure inside, these Bridges prone to fatigue damage, and fatigue damage often leads to the fracture of the structure of the bridge collapsed with sudden. In order to ensure the safety of the bridge in the passage, it is necessary to calculate the residual service life of the bridge by using the effective method to calculate the fatigue of the steel truss structure.

At first, the ANSYS finite element analysis software was used to model the steel truss structure in this paper, according to the relevant books data using steel truss bridge truss structure: a reasonable span length, internode length, truss height, connecting method and determine the truss bar material and sectional characteristic. Then, in order to add the uniformly distributed load of the two-stage constant load and the roadway load in the first stage load of the highway, the maximum stress bars of all kinds of rods were obtained by using ANSYS software. In all kinds of corresponding to the maximum stress bar deck protection continue to add lane load concentrated load on ANSYS software simulation has been run all kinds of bar end force size, the calculation results compared to the intensity of bar material design bar under the load of strength reliability. Finally, the stress amplitude is obtained by using the uniformly distributed load and the concentrated load of the load on the driveway. Through the s-n curve drawing stress amplitude, using the method of fatigue s-n curve bridge life calculation, and the use of fracture mechanics method and the reliability evaluation method for bridge life, finally comprehensive optimal solutions are obtained.

Through analysis and calculation, the simulation model established by ANSYS is reliable. The calculation parameters are more reasonable, the structural load factor is more comprehensive, and the simulation results are good. The s-n fatigue curve method can be used to predict the life of steel truss bridge, which has high precision and wide application prospect.

Keywords: steel truss bridge; Ansys modeling analysis; Fatigue problem of steel bridge; Life assessment

目录

摘要 1

第一章 绪论 3

1.1 疲劳问题的研究背景及意义 3

1.2疲劳的概念 4

1.3 桥梁剩余寿命概念 5

1.4 钢桥疲劳问题研究现状 6

1.5 疲劳分析方法 7

1.6 本文研究内容、方案及流程 12

第二章 钢桁架桥 13

2.1 钢桁架桥简介 13

2.2 钢桁架桥的特点 13

第三章 钢桁架桥的ANSYS建模 14

3.1 钢桁架桥节点ANSYS三维实体建模 14

3.2 模型结果分析 22

3.3 本章小结 24

第四章 钢桁架桥疲劳剩余寿命评估 25

4.1 S-N疲劳曲线法 25

4.2 基于断裂力学的寿命评估方法 29

4.3 可靠度方法 31

4.4 本章小结 32

第五章 有关桥梁剩余寿命计算实例 33

5.1 工程概况 33

5.2 计算结果 48

5.3 本章小结 49

第六章 全文总结与展望 50

6.1 总结 50

6.2 展望 50

6.3 致谢 51

参考文献： 52

绪论

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疲劳问题的研究背景及意义

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1.2疲劳的概念

1.2.1疲劳

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