【作者】 王慧东；

【导师】 强士中；

【作者基本信息】 西南交通大学 ， 桥梁与隧道工程， 2007， 博士

【摘要】 箱形截面优美的外形、良好的力学性能及构造功能，使得其被广泛地应用于桥梁工程上，然而，薄壁箱形梁在纵向弯曲时会产生剪力滞后效应，即剪力滞效应，不考虑剪力滞效应的影响，将会导致桥梁结构较高的安全风险甚至坍塌。剪力滞效应做为一个经典课题，国内外学者从20世纪20年代就开始研究，至今已有几十年的历史，尽管取得了一些成果，并且这些成果已部分地反映在各国的桥梁规范中，但亦有许多问题尚未得到解决。20世纪中叶的几次重大桥梁坍塌事故，引起了桥梁学者对箱形梁剪力滞效应的再次关注，从而开始了进一步的探讨与研究。本文阐述了箱形梁的受力特点、薄壁箱形梁剪力滞后效应的概念及目前解决剪力滞问题的主要理论和方法，探讨了这些理论和方法的适用性和局限性。导出了压弯荷载共同作用下箱梁剪力滞效应的三杆比拟杆法控制方程，并给出了边界条件；导出了简支梁和悬臂梁在竖向均布荷载及竖向集中荷载与轴向力共同作用下考虑剪力滞效应的正应力计算公式，将简支梁和悬臂梁在竖向均布荷载及竖向集中荷载作用下考虑剪力滞效应的正应力计算公式与在竖向均布荷载及竖向集中荷载与轴向力共同作用下考虑剪力滞效应的正应力计算公式统一起来，并将压弯荷载共同作用下箱梁剪力滞效应计算推广到多杆比拟法中，给出了控制方程；导出了压弯荷载共同作用下箱梁剪力滞效应的变分法控制方程，并给出了边界条件；导出了简支梁和悬臂梁在竖向均布荷载竖向集中荷载与轴向力共同作用下的考虑剪力滞效应的正应力计算公式及挠度计算公式，将简支梁和悬臂梁在竖向均布荷载及竖向集中荷载作用下的考虑剪力滞效应的正应力及挠度计算公式与在竖向均布荷载竖向集中荷载与轴向力共同作用下考虑剪力滞效应的正应力计算公式及挠度计算公式统一起来；用比拟杆法、变分法对压弯荷载共同作用下箱梁的剪力滞效应进行了研究。本文亦就悬臂梁中产生的负剪力滞进行了阐述，并分析了影响悬臂梁负剪力滞效应的因素。最后，对几座典型桥梁应用规范的方法、三杆比拟法、最小势能原理的成果和有限元法进行分析与对比研究，得出了一些结论，基于这些成果对箱形梁的设计给出了一些建议。更多还原

【Abstract】 The box girders have been widely used in the bridge engineering because their beautiful external shapes, good behaviors and structural functions, but they show the shear lag or negative shear lag effect when symmetry bending loads act longitudinally .If the effect of shear lag is neglected ,high risks up to collapse of bridges may take place . As a classic subject, shear lag effect has been studied by scholars all over the world past several decades, some conclusions have been achieved. The bridge codes and specifications in many countries have taken shear lag effect into account, but many problems with shear lag stay continuously. The bridge engineering disasters in the middle last century made the scholars pay more attention to shear lag effect again and farther research restarted.The box girder mechanical characters and the concept of shear lag are introduced in this dissertation, the theories and methods for solution to shear lag effect are discussed; Their suitability and constraint of use are discussed too. 3—bar simulation method governing equations with different boundary conditions are derived according to assumptions considering the compact-bending effect, and the solutions to simple bearing and cantilever girders under uniform and concentrated load are derived. The uniform formulas for simple bearing and cantilever girders under bending loads and compact-bending loads are constructed , the solution to normal stress of 3—bar simulation method for box girders is extrapolated to multi-bar simulation and governing equations are derived . General potential enery equations are constructed according to the principle of minimum potential energy based on the 3-degree distribution of longitudinal displacement along transverse direction and a set of governing differential equations with different boundary conditions are derived according to the energy equation considering the compact-bending effect, and the solutions to simple bearing and cantilever girders under uniform and concentrated load are derived. The uniform formulas for stress and deflection of simple bearing and cantilever girders under bending loads and compact-bending loads are constructed. Shear lag effect of box girders are studied with bar simulation、energy variation and FEM , verifications of these methods show that are believable . Negative shear lag effect is studied and the factors leading to negative shear lag are analyzed too .Some girders of bridges are studied and compared in the end according to the bridge specifications and the methods discussed in the dissertation . Some suggestions to the shear lag effect are given to the design of the box girders.更多还原