正交异性钢桥面板结构热点应力分析及可靠度评估

发布时间：2018-12-25 20:56

【摘要】：正交异性钢桥面板由于自重轻、节省钢材、抗扭刚度大、整体性好、承载能力高等优点,其作为整体式桥面体系在缆索承重体系的钢桥中得到广泛应用。然而,正交异性钢桥面板焊接结构中,钢桥面板与纵向加劲肋和横隔板之间连接的焊接节点焊趾处存在应力集中现象,在交通荷载直接作用下,焊接节点焊趾处容易发生结构破坏。本文以正交异性钢桥面板焊接节点为研究对象,对焊接节点焊趾处不同的结构热点应力确定方法进行比较分析,进而对其进行受力性能分析以及可靠度评估,本文主要的研究工作如下。利用有限元软件ANSYS分别建立了焊接节点的实体单元和壳单元有限元模型,在焊趾附近区域共划分七种尺寸单元网格,分别采用直接提取法、表面外推法和结构应力法计算正交异性钢桥面板焊接节点焊趾处的结构热点应力,比较分析不同方法计算结果的精度及其对有限元网格尺寸和单元类型的敏感性。研究结果表明,对于不同网格尺寸和单元类型的有限元模型,直接提取法和表面外推法获得的结构热点应力离散性较大,结构应力法计算的结构热点应力具有较好的—致性。基于结构应力法在确定焊趾附近合理的应力分布方面是一种有效的数值分析计算方法,考虑焊接节点自身材料属性和外部荷载条件的随机性,利用结构可靠度理论的概率分析方法对正交异性钢桥面板进行可靠度评估。首先,在已建立的焊接节点实体单元和壳单元有限元模型的基础上,分析结构应力计算结果在不同荷载作用下对单元类型和网格尺寸的敏感性。其次,根据焊接节点的抗力效应和荷载效应建立结构功能函数,其中,抗力效应为结构的材料强度,荷载效应以结构应力方法计算获得结构应力表示。最后,利用一次二阶矩结构可靠度分析方法计算焊接节点的可靠度指标和失效概率,通过与目标结构可靠度指标比较分析,对正交异性钢桥面板进行安全性评定。研究结构表明,在不同荷载作用下,结构应力法计算得到的结构应力对单元类型和网格尺寸不敏感,并且利用结构应力计算结果作为结构功能函数的随机变量能有效地对正交异性钢桥面板进行可靠度评估。
[Abstract]:Due to the advantages of light weight, saving steel, high torsional stiffness, good integrity and high bearing capacity, orthotropic steel deck is widely used in steel bridges with cable bearing system. However, in the orthotropic steel bridge panel welding structure, the stress concentration phenomenon exists at the spot welding toe of the welded joint between the steel deck plate and the longitudinal stiffened rib and the transverse partition plate, which is directly affected by the traffic load. The structure damage is easy to occur at the spot welding toe of welding joint. Taking the welded joints of orthotropic steel bridges as the research object, this paper makes a comparative analysis of the different structural hot spot stress determination methods at the welding joints and toes, and then analyzes the mechanical performance and reliability evaluation of the joints. The main research work of this paper is as follows. The finite element models of solid element and shell element of welded joint are established by using finite element software ANSYS. Seven sizes of element meshes are divided in the area near the weld toe, and the direct extraction method is used respectively. The surface extrapolation method and structural stress method are used to calculate the hot spot stress of orthotropic steel bridge face welded spot welding toe. The accuracy of different calculation methods and their sensitivity to finite element mesh size and element type are compared and analyzed. The results show that for the finite element models with different mesh sizes and element types, the structure hot spot stress obtained by direct extraction method and surface extrapolation method is more discrete, and the structural hot spot stress calculated by structural stress method has better-induced properties. The structural stress method is an effective numerical analysis method for determining the reasonable stress distribution near the weld toe, considering the randomness of the material properties of the welded joints and the external load conditions. The reliability of orthotropic steel bridge panels is evaluated by using the probability analysis method of structural reliability theory. Firstly, based on the established finite element model of welded joint solid element and shell element, the sensitivity of stress calculation results to element type and mesh size under different loads is analyzed. Secondly, according to the resistance effect and load effect of welded joints, the structural function is established, in which the resistance effect is the strength of the material of the structure, and the structural stress is expressed by the calculation of the load effect by the structural stress method. Finally, the reliability index and failure probability of welded joints are calculated by using the reliability analysis method of the first-order second-moment structure. The safety of orthotropic steel bridge face is evaluated by comparing with the reliability index of the target structure. It is shown that the structural stress calculated by the structural stress method is insensitive to the element type and mesh size under different loads. And the reliability of orthotropic steel bridge face can be evaluated effectively by using the structural stress calculation result as the random variable of the structural function.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U441;U443.31

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