基于空间整体分析下的下承式钢板梁桥稳定问题研究

发布时间：2018-08-29 16:07

【摘要】：近些年来,国家的基础设施建设正如火如荼的开展,特别是在公路和铁路建设中,我们看到了越来越多钢桥的身影,桥梁自身的结构形式也趋于多样化,设计水平及其施工技术愈加先进合理。这其中,常见的钢板梁桥更是伴随着中国铁路一路走来,见证着现如今中国铁路的迅猛发展。但是稳定性作为钢桥设计过程中的一个突出问题,倘若处理的不够得当就会造成比较严重的工程事故,当其作为一个整体发生失稳的时候,梁将产生侧向的弯曲以及发生宏观层面上的扭转变形。下承式钢板梁桥的主梁与桥面系共同构成了一个敞口框架,所以为了加强稳定性能,提供足够的强度作用,故而在横梁和主梁之间设置了肱板,这是从构造上弥补没有上平纵联所带来的稳定问题。但肱板这一构造,它所带来的结构强度以及结构自身的稳定性能,到底程度如何还需要进一步讨论。再者,传统的下承式钢板梁桥稳定问题的研究通常由于结构自身的复杂性,被分成整体稳定和局部稳定这两大部分分别进行计算,如今由于结构有限元技术的发展,可以把下承式钢板梁桥完全作为一个整体探讨其整体稳定问题。论文写作思路如下:首先通过翻阅与钢板梁桥相关的经典教材,公路、铁路规范以及相关文献。概括钢板梁桥稳定性问题计算方法以及与之相关的研究内容。分别总结规范中对公路钢板梁桥、铁路钢板梁桥局部以及整体稳定的规定。其次通过翻阅有限元书籍,总结有限元软件MIDAS关于平板单元有限元方程,板单元施加荷载方法,板单元结果分析,单元之间的边界条件与约束方程,应用有限元方法对结构进行弹性屈曲分析等内容,从而为下承式钢板梁桥利用有限元方法进行数值分析提供理论依据。然后运用数值计算的手段,为保证结构在发生整体失稳前不出现局部失稳,参照规范对结构局部稳定方面的规定,在规范规定的范畴内进一步分析下承式钢板梁桥的细部构造对结构局部稳定性产生的影响,从而得到满足规范局部稳定要求的有限元模型。最后对满足要求的有限元模型分别从有肱板和无肱板两个方面进行整体稳定性分析,探究宏观失稳模态下结构整体失稳的临界荷载,与规范规定的结构整体稳定内容进行计算匹配,从这两个方面计算得出的临界值上寻找差异性,从而可分析研究下承式钢板梁桥的整体稳定问题。论文结论如下:(1)对有无肱板这两种情况下的下承式钢板梁桥进行有限元分析后,得到的数据可知,当加上肱板以后,对于下承式钢板梁桥这样的仅由主梁与桥面系共同构成了一个敞口框架来说,进一步加强了它的稳定性能,其一可以对主梁的上翼缘板提供支撑作用,保证上翼缘板的稳定性能;其二可以起到横联的作用并减少或预防主梁的偏斜。这可从下承式钢板梁桥有无肱板这两种情况的屈曲模态图中得到印证,并且相应所能承受的临界荷载值有了一个较为明显的提高,从未加设肱板时的238.78 kN,到加设肱板后的306.51 kN。临界荷载值提升幅度为28%。(2)对加设肱板的下承式钢板梁桥的整体稳定验算中,从铁路规范中算得的限值为270 MPa,而通过有限元计算得到的全桥最大弯曲应力为279.52 MPa。两者进行比对可以得知,依据铁路规范验算得到的整体稳定性是偏于保守的,可以安全的应用在实际工程的相关检算当中。由于规范中对于结构的整体稳定性采用的是近似计算方法,所以通过对具体的结构进行有限元分析所得到的结果,进一步验证了规范规定对于下承式钢板梁桥整体稳定性验算的适用性。(3)运用公路规范,算得的弯扭屈曲临界弯矩为:M_(cr,z)=407.12kN.m,而根据有肱板的下承式钢板梁桥有限元计算结果,并依据2.2.1节式(2.36)算得的弯扭屈曲临界弯矩为:M_(cr)=388.42kN.m。结果对比公路规范规定算得值偏小,但是处在规范规定算得值±%5以内。两值进行比对可以得知,依据公路规范验算得到的整体稳定性是基本保守的,可以安全的应用在实际工程的相关检算当中。
[Abstract]:In recent years, the national infrastructure construction is in full swing. Especially in the highway and railway construction, we see more and more steel bridges, the structure of the bridge itself tends to be diversified, the design level and construction technology become more advanced and reasonable. Along the way, witness the rapid development of China's railway. But stability as a prominent problem in the design process of steel bridges, if not properly handled, will lead to more serious engineering accidents, when it as a whole occurs instability, the beam will produce lateral bending and macro-level torsion. Deformation. The main girder and the deck system of the through steel plate girder bridge constitute an open frame, so in order to strengthen the stability performance and provide enough strength, the brachial plate is set between the beam and the main girder, which is a structural compensation for the stability problem caused by the lack of vertical and horizontal connection. Furthermore, the traditional research on the stability of through steel plate girder bridges is usually divided into two parts: the overall stability and the local stability, which are calculated separately because of the complexity of the structure itself. This paper discusses the overall stability of through steel plate girder bridges as a whole. The main ideas of this paper are as follows: Firstly, by referring to the classical textbooks related to steel plate girder bridges, highway, railway codes and related literature, the paper summarizes the calculation methods of stability of steel plate girder bridges and related research contents. Secondly, the finite element software MIDAS is used to summarize the finite element equation of plate element, the method of loading plate element, the result analysis of plate element, the boundary condition and constraint equation between elements, and the finite element method is used to carry out the elasticity of the structure. In order to provide a theoretical basis for the numerical analysis of through steel plate girder bridges by using finite element method, the local buckling analysis is carried out by means of numerical calculation in order to ensure that no local buckling occurs before the overall buckling occurs. The influence of the details of the through steel plate girder bridge on the local stability of the structure is studied, and the finite element model which meets the local stability requirements of the code is obtained. Boundary load is calculated and matched with the structural stability content stipulated in the code, and the difference is found from the critical value calculated from these two aspects, so that the overall stability of through steel plate girder bridge can be analyzed and studied. The obtained data show that, when the brachial plate is added, the stability of an open frame composed of only the main girder and the deck system, such as through steel plate girder bridge, is further strengthened. This can be verified by the buckling modal diagrams of through steel plate girder bridges with or without brachial plates, and the corresponding critical load values have been significantly increased, from 238.78 kN without brachial plates to 306.51 kN. with brachial plates. (2) In the checking calculation of the overall stability of the through steel plate girder bridge with brachial plates, the limit value calculated from the railway code is 270 MPa, while the maximum bending stress calculated by the finite element method is 279.52 MPa. The results of finite element analysis of concrete structures further verify the applicability of the code for checking the overall stability of through steel plate girder bridges. (3) Highway use. According to the code, the critical moment of bending and torsional buckling is M_ (cr, z) = 407.12kN.m, while the critical moment of bending and torsional buckling is calculated according to the finite element results of through steel plate girder bridges with brachial plates and 2.2.1 knot (2.36). The result is smaller than that of highway code, but less than (+%) 5. The comparison of the two values shows that the overall stability calculated according to the highway code is basically conservative and can be safely applied to the relevant checking calculation of practical projects.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U441

【参考文献】