薄壁箱梁的畸变效应分析

发布时间：2019-01-26 12:18

【摘要】：箱形截面在桥梁建设中被越来越多地广泛采用，这不仅是由于箱形截面具有截面抗扭和抗弯刚度大，而且箱形截面梁具有结构自重小等诸多的优点。但是箱形梁在承受偏心荷载作用时，除了引起截面刚性扭转外，还会产生截面约束扭转，也就是畸变变形。在畸变变形中，箱形截面产生翘曲应力，并且翘曲应力在箱形梁的自身弯曲应力中所占比例很大。因而在箱形截面梁的设计工作中，畸变效应必须加以考虑，是不容忽视的。箱形梁的畸变微分方程大致有两类表达形式：一是用畸变后的扭转角（畸变角）来表示的畸变微分方程，一类是用畸变挠度表示的畸变微分方程。本论文着重对用畸变角表示的畸变微分方程进行了详细的推导。本论文所做的工作有以下几个方面。首先，对箱形截面梁所承受的偏心荷载进行分解，得到用以计算的畸变荷载，畸变荷载包含了竖向和水平两种畸变荷载形式。并分析了箱形梁在斜支撑（三条腿）情况下，由于箱梁自重而产生的畸变荷载，这类畸变荷载属于支座反力，需要单独分析。其次利用能量变分原理和静力平衡法推导出单室矩形截面箱梁的畸变微分方程，并且对用畸变角表示的微分方程和用挠度表示的微分方程进行了比较，得出了二者之间的相互转换关系。箱形梁的畸变微分方程与弹性基地梁的挠曲微分方程有相似的表达式，由此可通过求解弹性基地梁的挠度来确定箱形梁的畸变角。接着对某一单室矩形箱梁在偏心均布荷载下进行理论计算和建模分析。利用两种不同方法推导的微分方程对算例进行计算，得到两种不同的计算结果，再利用ANSYS的分析结果对两者进行比较，，从而得出利用静力平衡法推导出的畸变微分方程更加精确。最后，研究了横隔板的设置对箱形梁畸变的影响作用。在集中偏心荷载和均布偏心荷载作用下，横隔板的设置对箱形梁的畸变影响不同。在均布荷载作用下，横隔板的设置对减小畸变有明显的效果，设置一定数量的横隔板时，就能有效地减小畸变的影响作用。但在集中荷载作用下，在集中荷载以外截面的横隔板对集中荷载截面的畸变影响不大，只在集中荷载截面处设置横隔板就能达到想要的效果。目前，桥梁设计者已经认识到箱形梁畸变的重要性，逐步的分析和完善了箱形梁畸变效应的影响作用。本论文中通过对单室矩形截面箱梁的畸变效应分析，也进一步说明了对薄壁箱梁畸变效应进行深入研究的必要性。
[Abstract]:Box section is more and more widely used in bridge construction, which is not only due to the torsion and bending stiffness of box section, but also to the advantages of box section beam with low structural weight and so on. However, when the box beam is subjected to eccentric load, it will not only cause the rigid torsion of the section, but also produce the section constrained torsion, that is, distortion and deformation. In the distortion deformation, the box section produces warpage stress, and the warpage stress accounts for a large proportion of the bending stress of the box beam. Therefore, in the design of box section beam, the distortion effect must be considered and can not be ignored. There are two kinds of differential equations of distortion for box beams: one is the distortion differential equation expressed by the distorted torsion angle (distortion angle); the other is the distortion differential equation expressed by the distortion deflection. In this paper, the distortion differential equation represented by distortion angle is derived in detail. The work done in this paper has the following aspects. Firstly, the eccentric load of box section beam is decomposed, and the distortion load is obtained, which includes vertical and horizontal distortion loads. The distortion load caused by the dead weight of the box girder under the condition of oblique bracing (three legs) is analyzed. This kind of distortion load belongs to the support reaction force and needs to be analyzed separately. Secondly, the differential equation of distortion of box girder with single chamber rectangular section is derived by energy variational principle and static equilibrium method, and the differential equation expressed by distortion angle is compared with the differential equation expressed by deflection. The relationship between them is obtained. The distortion differential equation of box beam is similar to that of elastic base beam, so the distortion angle of box beam can be determined by solving the deflection of elastic base beam. Then the theoretical calculation and modeling analysis of a single-chamber rectangular box girder under eccentrically distributed load are carried out. The differential equations derived by two different methods are used to calculate the numerical examples, and two different results are obtained, and then the two results are compared by using the analysis results of ANSYS. It is concluded that the distortion differential equation derived by the static equilibrium method is more accurate. Finally, the effect of the setting of transverse diaphragm on the distortion of box beam is studied. Under the action of concentrated eccentricity load and uniformly distributed eccentric load, the distortion of box beam is influenced by the setting of transverse diaphragm. Under uniform load, the setting of transverse diaphragm has obvious effect on reducing distortion. When a certain number of transverse partitions are set, the effect of distortion can be effectively reduced. However, under the action of concentrated load, the cross-spacer with cross-section outside concentrated load has little effect on the distortion of concentrated load section, and the desired effect can only be achieved by setting transverse diaphragm at the section of concentrated load. At present, bridge designers have realized the importance of box beam distortion, and gradually analyzed and improved the box beam distortion effect. In this paper, the distortion effect of single-chamber rectangular section box girder is analyzed, and the necessity of studying the distortion effect of thin-walled box girder is further explained.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U441;U448.213

【参考文献】