基于热点应力法的正交异性桥面板的疲劳性能研究

发布时间：2018-08-03 20:40

【摘要】：正交异性钢桥面板是由相互垂直的纵、横向加劲肋和桥面板焊接而成,具有自重轻、极限承载力大、施工周期短、结构美观等优点,因此被广泛应用于国内外的大、中跨径桥梁中。但正交异性钢桥面板结构构造复杂,焊缝长度大,又加上焊接造成的残余应力,结构本身存在的缺陷以及施工质量和直接承受车轮载荷的反复作用等综合因素的影响,正交异性钢桥面板易于遭受疲劳损伤。目前各国钢桥的疲劳验算多采用名义应力法,该方法适用于结构较为简单的情况,对复杂的正交异性桥面板结构效果不理想,疲劳寿命用名义应力表示时,结果离散性很大,很难给出精确的S-N曲线图。热点应力法相对于名义应力法,能更好的适应复杂结构,逐渐成为了分析焊缝疲劳的重要方法之一,但其在正交异性钢桥面板上的应用还不多。本文以此为出发点,研究热点应力法在正交异性钢桥面板焊缝疲劳分析中的应用。本文基于苏通大桥桥面板进行了ANSYS建模,分别分析了其各典型薄弱部位的轮载不利加载位置,明确了薄弱部位的应力集中状况,为进行正交异性钢桥面板的有限元分析提供了建模和加载分析的参考方法。正交异性钢桥面板焊缝复杂,本文选取了四个热点位置,即RD (Rib-to-Deck,纵肋与面板连接处)面板焊趾、RD面板焊根、RD纵肋焊趾、RF (Rib-to-Floorbea m,纵肋与横隔板连接处)焊趾,对它们进行了精细有限元计算,研究了有限元网格对其应力值和热点外推区应力分布稳定性的影响,建议了实际工程中建模分析时合适的有限元网格尺寸。对于热点在焊趾处的情况,各规范中已有相关的热点应力表面外推计算方法的规定,但桥面板中,RD面板焊根处的应力集中情况更为严重,产生裂纹的破坏性更大,对于此种热点在焊根处的情况,现有各规范还缺乏相关规定。本文针对选取的四个热点位置,进行了详细的热点应力表面外推计算方法的推导,并与现有规范进行了比较,三个焊趾热点位置的推导结果与规范较相符,但它们各自适用的规范有所不同。对于RD面板焊根位置,通过分析,其相关结论与焊趾区域类似,但其外推点位置与现有规范有比较大的差异,不能将现有规范用于计算RD面板焊根热点应力。同时,焊缝弹性模量的变化对正交异性钢桥面板各热点部位的热点应力表面外推计算方法没有影响,因此工程实际中建模时可以采用焊缝与母材等强的简便方法。最后,本文使用推导出的正交异性钢桥面板各热点部位热点应力计算公式,对正交异性钢桥面板的几大基本参数进行了分析,发现面板厚度对热点应力的影响程度最大,因此可以通过提高面板厚度来降低热点应力,从而提高正交异性钢桥面板的疲劳寿命。
[Abstract]:Orthotropic steel bridge panels are welded by vertical, transverse stiffened ribs and deck plates, which have the advantages of light weight, large ultimate bearing capacity, short construction period and beautiful structure, so they are widely used at home and abroad. Middle span bridge. However, the structure of orthotropic steel bridge is complicated, the length of weld seam is large, the residual stress caused by welding, the defects of the structure itself, the quality of construction and the repeated action of bearing wheel load directly, and so on. Orthotropic steel bridge panels are prone to fatigue damage. At present, nominal stress method is widely used in fatigue checking calculation of steel bridges in many countries. This method is suitable for simple structure. The effect on complex orthotropic deck slab structure is not ideal. When fatigue life is expressed by nominal stress, the result is very discrete. It is difficult to give accurate S-N curves. Compared with the nominal stress method, the hot spot stress method is more suitable for complex structures, and has gradually become one of the important methods of weld fatigue analysis, but its application on orthotropic steel bridge face is not much. In this paper, the application of hot spot stress method to fatigue analysis of orthotropic steel bridge face weld is studied. In this paper, based on the ANSYS modeling of Sutong Bridge deck, the unfavorable loading position of each typical weak part of the bridge is analyzed, and the stress concentration in the weak part is determined. The method of modeling and loading analysis is provided for the finite element analysis of orthotropic steel bridge panel. The welding seam of orthotropic steel bridge face plate is complicated. In this paper, four hot spots are selected, that is, R D (Rib-to-Deck, longitudinal rib and panel joint), R D welding toe, RF (Rib-to-Floorbea m) for R D longitudinal rib welding toe. The influence of finite element mesh on stress value and stress distribution stability in hot extrapolation region is studied, and the appropriate finite element mesh size for modeling and analysis in practical engineering is suggested. In the case of hot spot at the weld toe, there are some relevant calculation methods for the hot spot stress surface extrapolation in each specification, but the stress concentration at the welding root of the bridge deck plate is more serious and the cracks are more destructive. For such hot spot in the solder root, the existing specifications are still lack of relevant provisions. In this paper, the extrapolation method of hot spot stress surface is deduced for the four hot spots selected, and compared with the existing codes, the results of the three hot spot locations of welding toe are in good agreement with the code. But they each apply different norms. According to the analysis of the root position of Rd panel welding, the conclusion is similar to that of the weld toe region, but the extrapolation point position is quite different from the existing specification, so it can not be used to calculate the hot spot stress of R D panel welding root. At the same time, the variation of elastic modulus of welding seam has no effect on the extrapolation method of hot spot stress surface in each hot spot of orthotropic steel bridge panel, so the simple method of welding seam and base metal can be used in engineering practice. Finally, by using the formula for calculating hot spot stress of orthotropic steel bridge panel, several basic parameters of orthotropic steel bridge face plate are analyzed. It is found that the thickness of orthotropic steel bridge panel has the greatest influence on hot spot stress. Therefore, the fatigue life of orthotropic steel bridge panel can be improved by increasing the thickness of the plate to reduce the stress of hot spot.
【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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