【作者】 郑为明；

【导师】 陈燊；

【作者基本信息】 福州大学 ， 桥梁与隧道工程， 2005， 硕士

【摘要】 近年来，箱形结构现代化施工方法和分析理论取得不断进步，箱形结构已由厚壁、窄箱向薄壁、宽箱、少横隔板甚至无横隔板发展，箱梁的畸变影响越来越突出。本文所研究的上下行分层矮斜拉连续箱梁桥属于无横隔板的双层新型结构。目前，对该桥型结构的研究很少。由于具有广阔的应用前景，因此对其进行静力分析和截面畸变效应的研究显得尤为重要。本文以双层矮斜拉连续箱梁桥为研究对象，进行桥型的拟实用设计，并利用大型通用有限元软件ANSYS建立结构分析空间模型，分析得到主梁在恒载、预应力荷载以及各工况活载作用下各控制截面的节点应力、挠度以及索力的变化情况。分析结果表明：(1) 在恒载和预应力荷载作用下顶底板的应力分布规律基本相同，预应力对改善主梁的内力分布效果明显。采用新规范车道荷载的计算模式进行空间桥梁结构整体布载计算时，车道荷载中的集中荷载标准值将引起局部的应力集中，尤其是对宽箱、薄壁的箱梁结构，这种应力集中的现象尤为明显，截面正应力沿横桥向分布很不均匀，与旧规范有所不同，在设计时应给予充分重视。(2) 斜拉索能够有效地减小主梁的最大正负弯矩效应，削减应力峰值，改善整个桥梁结构的内力分布，其作用相当于一个弹性支座。斜拉索的存在使主梁的竖向刚度得到明显的加强，计算和试验均表明，该桥具有进一步增大跨径的潜力。 (3) 由活载引起的拉索索力占总索力(活载+恒载)的比重较小，即斜拉索的应力幅值较小，索疲劳现象不突出，故其容许应力可取0.6，以提高斜拉索的利用率。此外，本文还探讨了不同的塔高、拉索索力等主要设计参数对全桥力学行为的影响。结果表明，塔高变小，主梁竖向刚度降低，挠度增大。初张拉索力值的变化是影响主梁变形及其内力分布的主要因素，其影响效果要比塔高的变化对主梁内力分布的影响来得明显，可通过调整初张拉索力设计值来实现降低塔高的目的。为了验证理论分析的可靠性，对所设计的桥梁结构型式进行缩尺有机玻璃模型试验，得到上下行矮斜拉连续箱梁桥在各种试验工况下的应力应变、挠度、索力的变化情况，据此核验和完善有限元模型。试验测定了各主要测试断面的畸变角，并提出畸变角测试的修正方法。最后分析得到该桥梁结构的静力特性以及各主要断面的畸变效应。更多还原

【Abstract】 Recently, with the advancement of modernized construction method and analysis theory, the box-section structure has developed from thick-wall and narrow-box to thin-wall, wide-box and few diaphragm, even non-diaphragm. And further, the distortion effects of box-girder become more and more predominant. In this thesis a new double decked, separating up and down vehicles, non-diaphragm and partially cable-stayed bridge structure is presented. The research on this type of bridge is rarely dealt with so far. Therefore, it is very important to carry out the static analysis and study of distortion effects for the structure, because of widely applied prospects.Firstly, a practical design of double decked continuous box-girder bridge has been done and then the large and universal finite element software ANSYS has been used to build a spatial model for the structural analysis. As results of analysis, the nodal stress, deflection and the change of cable force under dead load, prestressing force and live load on main sections are gained, and come to the conclusion that: (a) The stress distribution rule of the top slab or the bottom plate under the dead load is similar to that under the prestressing force. The prestress can improve the distribution of internal force of the girder remarkably. When the theoretical mode of lane loading in the new Norm is adopted to calculate the spatial bridge structure, the standard value of concentrated load in lane loading will cause the stress concentration, especially obvious for wide-box and thin-wall box-section structure. The transverse distribution of stress is uneven extraordinarily. In view of the difference from the old Norm, designers should pay much attention to it. (b) The stay cable can reduce the maximum sagging and negative moment effectively, cut the peak value of stress and improve the internal force distribution of whole bridge structure. Its function is equivalent to an elastic support. The stay cable make the vertical rigidity of girder strengthen markedly. The numerical results and model test both indicate that it is potential to increase the bridge span further.(c) The cable force caused by live load accounts for relatively little proportion of the total cable force. That is to say, the stress amplitude of cable is relatively small. The fatigue phenomenon of it is not outstanding, hence the allowable stress can take 0.6σu, which will increase the utilization ratio of stay cable.In addition, some of the main design parameters such as the tower height and the cable force which influence on the whole structure are still discussed. The results indicate that, with the decrease of the tower height, the vertical rigidity of girder will fall and the deflection will increase. The change of initial tensioning cable force is a main influencing factor on the deflection and the distribution of internal force of the girder. Its influence effect is more obvious than that of the change of tower height. So the purpose of reducing <WP=4>the tower height can be achieved by an adjustment of the initial tensioning cable force. In order to verify the reliability of theoretical analysis, the scaled plexiglass model test for the designed bridge structure form has been carried out. The values of stress, strain, deflection and the change of cable force in the bridge under different work conditions have been determined through the test. On these grounds, the finite element model has been checked up and perfected. Furthermore, a new amending method was put forward to the measurement of the distortion angle. By means of further analysis, the static distribution characteristic and distortion effects of every main test section of this bridge structure have been obtained.更多还原