基于主S-N曲线法的典型钢桥焊接节点疲劳寿命评估
发布时间：2019-01-01 16:20
【摘要】：钢桥由于长期受到交通荷载和环境因素的综合作用,承受大量不同应力幅值的应力循环,容易导致疲劳损伤和破坏,而焊接节点的疲劳破坏是钢桥断裂失效的主要原因之一。因此,及时准确地进行钢桥焊接节点疲劳寿命评估尤为重要。 名义应力法是最简单和最常用的钢桥焊接构件疲劳评估方法,普遍存在于各国及协会的钢桥疲劳设计规范,如我国钢结构设计规范GB50017、英国规范BS5400、欧洲规范Eurocode3.美国国家公路与运输协会(AASHTO)标准、国际焊接学会(ⅡW)标准等。然而,限于疲劳试验数据的有限性,现有规范难以涵盖所有焊接类型,导致疲劳寿命评估过程具有一定的主观性。此外,由于名义应力法没有考虑焊接构件的应力集中效应,评估结果往往过于保守。研究者又提出了表面外推的热点应力法,热点应力法考虑了焊接部位的应力集中,减少了选择S-N曲线的难度,从而提高了焊接构件的疲劳寿命评估精度。但是,大量的研究表明,在焊接构件的有限元应力分析过程中,基于表面外推确定的结构热点应力表现出较大的网格敏感性。基于上述考虑,Dong根据基本的力学原理,结合热点应力法,并考虑应力沿焊接构件厚度方向分布特点,提出了一种网格不敏感的结构应力确定方法。基于网格不敏感的结构应力计算方法和断裂力学理论,发展了主S-N曲线疲劳模型,并已成功应用于海洋平台管道、压力容器等结构的焊接节点疲劳寿命评估。主S-N曲线法综合考虑了应力集中、构件厚度、荷载模式等的综合作用,所有钢结构焊接构件都适用于同一条主S-N曲线,有效解决了焊接构件疲劳寿命评估现存的结构热点应力确定随机性和S-N曲线选择受限性的问题。 本文基于主S-N曲线法,利用有限元分析软件ANSYS,通过有限元分析及相应的后处理,对典型的钢桥焊接构件进行疲劳寿命评估,对主S-N曲线法在钢桥典型焊接构件疲劳寿命评估中的适用性、单元类型选择、单元尺寸的划分、焊缝的模拟方法、计算精度等进行了比较分析研究。对在规范中分类不同、长度分别为200mm和60mn的纵向角接节点疲劳寿命评估过程中,着重研究了同一主S-N曲线对分类不同的两个焊接节点的适用性,以及实体单元和壳单元两种单元类型对疲劳评估结果的影响。利用主S-N曲线法对带有开口肋的正交异性钢桥面板焊接节点进行疲劳寿命评估时,对采用不同焊缝模拟方法的模型均划分四种单元尺寸，研究重点在于不同的单元尺寸以及不同焊缝的模拟方法对疲劳评估结果的影响。 研究结果表明,结构应力的计算具有很好的网格不敏感性,后续的疲劳寿命评估结果也具有较稳定的结果；同一条主S-N曲线可用于不同分类的钢桥焊接节点的疲劳寿命评估：综合考虑各有限元模拟方法的精度及可行性,运用主S-N曲线法对钢桥焊接节点的疲劳寿命时,倾斜的壳单元模拟焊缝是一种较适合的模拟方法。
[Abstract]:Because of the comprehensive action of the traffic load and the environmental factors for a long time, the steel bridge can bear a large number of stress cycles with different stress amplitude values, which can lead to fatigue damage and damage, and the fatigue failure of the welding joints is one of the main causes of the failure of the steel bridge. Therefore, it is very important to evaluate the fatigue life of the steel bridge welding joints in a timely and accurate manner. The nominal stress method is the most simple and most commonly used steel bridge welding component fatigue assessment method, which is widely used in the steel bridge fatigue design specifications of countries and associations, such as the Code for Design of Steel Structures of China (GB50017), the British Standard BS5400, and the European Specification Eurocode. 3. American National Highway and Transportation Association (AASHTO) standard, International Welding Society (鈪，
本文编号：2397807
[Abstract]:Because of the comprehensive action of the traffic load and the environmental factors for a long time, the steel bridge can bear a large number of stress cycles with different stress amplitude values, which can lead to fatigue damage and damage, and the fatigue failure of the welding joints is one of the main causes of the failure of the steel bridge. Therefore, it is very important to evaluate the fatigue life of the steel bridge welding joints in a timely and accurate manner. The nominal stress method is the most simple and most commonly used steel bridge welding component fatigue assessment method, which is widely used in the steel bridge fatigue design specifications of countries and associations, such as the Code for Design of Steel Structures of China (GB50017), the British Standard BS5400, and the European Specification Eurocode. 3. American National Highway and Transportation Association (AASHTO) standard, International Welding Society (鈪，
本文编号：2397807
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