单箱三室箱梁在正对称荷载作用下局部畸变效应的理论研究

发布时间：2018-03-15 04:13

本文选题：三室箱梁　切入点：数值模型　出处：《兰州交通大学》2015年硕士论文　论文类型：学位论文

【摘要】：薄壁箱形截面梁在客运专线中的广泛使用,使得局部畸变效应在桥梁结构设计和受力分析越来越受人们重视。从理论推导和有限元数值模拟相结合对单箱三室箱梁在正对称荷载作用下基于闭口薄壁杆件理论的局部畸变效应的相关问题,进行了大量对比分析及研究,主要研究内容如下:(1)针对单箱三室箱梁在中腹板对称加载模式和边腹板对称加载模式来研究正对称作用下的受力情况。通过将单箱三室箱梁在中腹板对称加载模式下的荷载分解可看出,箱梁截面总体可看做约束扭转、畸变效应与剪力滞效应的组合变形;本文通过截开单箱三室箱形梁截面,截开后单室截面上的畸变竖向荷载与等效荷载计算公式利用截面剪力流平衡来推导出,以此为基础利用弹性地基比拟法可得到中腹板对称模式下单箱三室截面的约束扭转、畸变效应与剪力滞效应等组合变形下的应力;而边腹板对称加载模式下的单箱三室箱梁可通过荷载分解成中腹板对称加载模式进行计算。(2)针对单箱三室截面的简支梁和悬臂梁在中腹板对称加载模式下,数值模型采用ANSYS中SHELL63单元建立。数值解是通过叠加数值模型中提取的应力值得到的,并对畸变纵向应力及畸变横向应力解析解与数值解分别从(1)横向:不同截面各关键点部位;(2)纵向:各关键点部位沿跨度方向上的分布等两方面进行了大量的对比分析,结论如下:解析解和数值解无论从数值还是变化规律均基本吻合,证实了本文中相关理论推导是正确性与精确性。(3)针对单箱三室箱梁在边腹板对称加载模式下,利用荷载分解的方法将其等效成中腹板对称加载模式,单箱三室箱形梁截面局部畸变纵向应力及畸变横向应力的解析解与数值解进行了对比分析,分析结果表明,解析解和数值解基本吻合,同时说明,中腹板对称加载模式与边腹板对称加载模式利用荷载分解的方法相互等效的方法是可行的,同时也证明了本文相关理论推导的正确性。(4)本文中引入了畸变率的概念为了更加清晰的反映畸变应力占考虑剪力滞效应的弯曲应力的比值的大小。通过对截面畸变率的分析得到结论如下:单箱三室截面最大的畸变率出现在顶板悬臂部位,而畸变率最小的部位为顶板和边腹板交接处。中腹板对称加载模式下,简支梁L/2截面最小畸变率为15.21%,最大畸变率为43.7%;悬臂梁L/8截面最小畸变率为12.52%,最大畸变率为70.57%。边腹板对称加载模式下,简支梁L/2截面最小畸变率为6.42%,最大畸变率为22.4%;悬臂梁L/8截面最小畸变率为6.85%,最大畸变率为38.83%。结果表明,单箱三室箱梁在正对称加载模式下个别部位畸变率相对较大,在结构计算中应予以重视,同时,正对称荷载作用下荷载在横截面上分布越靠近顶板中心,截面局部畸变效应越明显。
[Abstract]:The wide use of thin-walled box section beam in passenger dedicated line, People pay more and more attention to local distortion effect in the design and stress analysis of bridge structure. Based on closed thin-walled member mechanism of single box and three-room box girder under normal symmetric load, the theoretical derivation and finite element numerical simulation are combined. On the related problems of local distortion effect, A large number of comparative analyses and studies have been carried out. The main contents of this study are as follows: (1) in view of the symmetrical loading mode of the single box and three chambers box girder under the symmetrical loading mode of the middle web and the symmetrical loading mode of the edge web plate, the loading modes of the single box and three room box girder under the normal symmetrical action are studied by using the symmetrical loading mode of the single box and three chambers box girder in the middle web. As can be seen from the decomposition of the load under the formula, The cross section of box girder can be regarded as the combined deformation of restrained torsion, distortion effect and shear lag effect. The formula for calculating the distorted vertical load and equivalent load on the section of a single chamber after cutting is derived by using the cross-section shear flow balance. Based on this formula, the constrained torsion of the three-compartment section of the order box can be obtained by using the elastic foundation analogy method. The stress under the combined deformation such as distortion effect and shear lag effect; The single box and three compartment box girder under symmetrical loading mode can be decomposed into the symmetrical loading mode of the middle web plate to calculate. (2) for the simple supported beam and cantilever beam of the single box and three compartment section under the symmetrical loading mode of the middle web, the single box and three compartment section of the box can be calculated under the symmetrical loading mode of the middle web. The numerical model is established by SHELL63 element in ANSYS. The numerical solution is worth the stress extracted from the superposition numerical model. The analytical solution and numerical solution of distortion longitudinal stress and distortion transverse stress are compared and analyzed respectively from two aspects: transverse: different key points of different sections and distribution of key points along the span direction, etc. The conclusions are as follows: both the analytical solution and the numerical solution are in good agreement with each other, which proves that the theoretical derivation in this paper is correct and accurate. By using the method of load decomposition, it is equivalent to the symmetrical loading mode of middle web. The analytical and numerical solutions of local distortion longitudinal stress and distortion transverse stress of single box and three compartment box beam are compared and analyzed. The results show that, The analytical and numerical solutions are in good agreement with each other. At the same time, it is shown that it is feasible to use the method of load decomposition for the symmetric loading mode of the mesosecond and the symmetrical loading of the edge web, which is equivalent to each other by the method of load decomposition. It also proves the correctness of the theoretical derivation in this paper. (4) the concept of distortion rate is introduced in this paper in order to more clearly reflect the magnitude of the ratio of distortion stress to the bending stress considering shear lag effect. The conclusions are as follows: the maximum distortion rate of the section of a single box and three chambers appears in the cantilever part of the roof. The lowest distortion rate is at the junction of the top plate and the edge web. Under the symmetrical loading mode of the middle web, The minimum distortion rate of L- / 2 section of simply supported beam is 15.21, the maximum distortion rate is 43.7, the minimum distortion rate of L- / 8 section of cantilever beam is 12.52 and the maximum distortion rate is 70.57. The minimum distortion rate of L / 2 section is 6.42 and the maximum distortion rate is 22.40.The minimum distortion rate of cantilever beam L / 8 section is 6.85 and the maximum distortion rate is 38.83.The results show that the distortion rate of individual parts of single box and three chambers box girder is relatively large in normal symmetric loading mode. At the same time, the distribution of the load on the cross section is closer to the center of the roof, and the local distortion effect of the section is more obvious.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U441

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