大跨钢桥疲劳裂纹扩展的数值模拟研究

发布时间：2018-04-16 22:40

本文选题：裂纹扩展 + 数值模拟　；参考：《东南大学》2015年硕士论文

【摘要】：疲劳破坏是钢桥构件和其连接细节的典型破坏模式之一,疲劳裂纹(缝)的萌生和扩展不仅影响到结构的安全,也引发了大量的后期养护费用。因此,科学准确地预测裂纹的扩展对于疲劳敏感部位的维修和加固具有重要意义。本文针对大跨斜拉桥的若干疲劳易损细节,研究了随机荷载作用下疲劳裂纹扩展的数值模拟方法,所完成的主要工作如下：(1)疲劳裂纹及其扩展的断裂力学理论及方法研究。介绍了裂纹扩展的三种模式及其成因,对裂尖渐进场的描述方法、断裂参数的常用计算方法、裂纹扩展模型、裂纹扩展的数值模拟方法及其适用性进行了对比分析。(2)提出了随机车载场和环境温度作用下的大跨钢桥疲劳裂纹扩展的数值模拟方法。通过桥梁收费系统和健康监控系统的实测数据,建立了一种面向疲劳分析的精细化车辆荷载概率模型以及环境温度模型。基于多尺度建模和子模型技术,采用最小应变能密度因子方法判定复合裂纹的扩展方向,应用局部网格重划分实现了疲劳裂纹扩展的数值模拟。(3)通过实桥检测,对斜拉桥钢箱梁纵隔板开裂情况进行了统计分析,研究了裂纹的形态、分布特点及扩展规律。通过有限元分析,研究了纵隔板的作用及其损伤后对桥梁性能的影响,探讨了纵隔板节点区域开裂的原因,并发现较大的应力幅和交变荷载是裂纹萌生及扩展的主要原因。在此基础上,通过概率有限元分析,对润扬斜拉桥跨中纵隔板节点区域的疲劳寿命进行了预测,其结果与实桥检测结果基本吻合。(4)基于本文提出的裂纹扩展的模拟方法,对润扬斜拉桥钢箱梁正交异性桥面板的不同部位进行了裂纹扩展分析：研究了裂纹扩展中各裂纹模式的贡献,得到了应力强度因子的时程曲线。基于线弹性断裂力学,对各细节的裂纹扩展寿命进行了预测。上述工作为研究大跨钢桥在运营阶段的疲劳损伤机理以及推演裂纹的萌生、扩展过程等问题提供了有效的手段,可为大跨钢桥的优化设计、维护方案和加固策略提供参考。
[Abstract]:Fatigue failure is one of the typical failure modes of steel bridge members and their connection details. The initiation and propagation of fatigue cracks (joints) not only affect the safety of structures, but also lead to a large amount of later maintenance costs.Therefore, scientific and accurate prediction of crack propagation is of great significance for the maintenance and reinforcement of fatigue sensitive sites.In this paper, the numerical simulation method of fatigue crack propagation under random load is studied for some fatigue vulnerability details of long-span cable-stayed bridge. The main work accomplished is as follows: 1) the theory and method of fracture mechanics of fatigue crack and its propagation.This paper introduces three modes of crack growth and their causes, the description of progressive field of crack tip, the commonly used calculation methods of fracture parameters, and the crack propagation model.The numerical simulation method of crack growth and its applicability are compared and analyzed. (2) A numerical simulation method for fatigue crack propagation of long span steel bridges under the action of random vehicle field and ambient temperature is proposed.Based on the measured data of bridge toll collection system and health monitoring system, a refined vehicle load probability model and environmental temperature model for fatigue analysis are established.Based on the technique of multi-scale modeling and sub-model, the minimum strain energy density factor method is used to determine the propagation direction of composite crack, and the numerical simulation of fatigue crack propagation is realized by using local mesh re-division.The cracking of the steel box girder of cable-stayed bridge is analyzed statistically, and the shape, distribution and propagation of the crack are studied.Through finite element analysis, the effects of mediastinal plate and its damage on bridge performance are studied, and the causes of cracking in the joint region of mediastinal plate are discussed. It is found that large stress amplitude and alternating load are the main causes of crack initiation and propagation.On this basis, through the probabilistic finite element analysis, the fatigue life of the middle mediastinal plate joint area of the Runyang cable-stayed bridge is predicted. The results are in good agreement with the real bridge detection results. (4) based on the simulation method proposed in this paper, the crack propagation is simulated.Crack propagation analysis of different parts of orthotropic deck plate of steel box girder of Runyang cable-stayed bridge is carried out. The contribution of crack modes in crack propagation is studied and the time-history curve of stress intensity factor is obtained.Based on the linear elastic fracture mechanics, the crack propagation life of each detail is predicted.The above work provides an effective means for studying the fatigue damage mechanism, crack initiation and propagation process of long span steel bridge in operation stage, and can be used as a reference for the optimization design, maintenance scheme and reinforcement strategy of long span steel bridge.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U441.4

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