【作者】 覃嘉仕；

【导师】 李忠献；

【作者基本信息】 天津大学 ， 结构工程， 2005， 硕士

【摘要】 曲线箱梁广泛应用于高速公路桥、铁路桥和城市立交、高架桥中。由于其几何形状的复杂性,除了常规结构的拉压、弯曲、扭转等行为外,曲线箱型梁还会出现横截面剪力滞效应。设计中忽视了剪力滞问题,将会影响桥梁的使用安全,我国对箱梁剪力滞研究起步较晚,现行桥梁设计中关于曲线箱梁的剪力滞计算仍仅限于学术讨论。本文作者利用板壳有限元分析方法,建立单箱单室箱梁板壳有限元计算模型,并且通过试验进一步考察了曲线箱梁弹性阶段的剪力滞后现象和非线性受力行为,主要内容如下:针对曲线箱梁的结构特性和剪力滞后分析要求,采用8结点平面壳单元建立空间有限元模型,并且运用FORTRAN语言开发了相应空间有限元程序,经过经典算例验证,结果吻合良好,说明程序的可靠性和适用性;通过分析尝试更进一步揭示箱梁剪力滞后现象产生的原因;根据曲线箱梁中内外侧腹板受力不均匀的特点,对现有曲线箱梁剪力滞系数的定义试探性提出建议,可以较好地区分由于扭转和剪力滞后导致的顶板正应力不均匀分布状况;为了更好的考察预应力对剪力滞的影响,首先应用空间矢量理论分析了预应力曲线梁中预应力束的作用特点,采用等效荷载法考虑了弹性阶段预应力对曲线箱梁剪力滞后的影响;应用ANSYS有限元建立分离式钢筋混凝土模型,对本次试验的曲线箱梁非线性特性进行分析;通过预应力混凝土模型试验和理论的对比,分析了试验和理论中可能存在的问题。计算和试验研究结果表明:(1)箱梁剪力滞现象是由于纵向剪应力变化不均匀引起的;(2)预应力作用使得箱梁跨中截面剪力滞后系数减小,梁端附近剪力滞系数增大;(3)利用ANSYS进行的非线性有限元分析得出试验结果基本吻合,证明建模方法使合理可行的。更多还原

【Abstract】 Curved box-girder is widely used for modern highway bridges, railway bridges,interchanges and viaducts. Due to geometric complexity of curved box-girder,cross-section warping and shear lag effect will occur during the service life besidesconventional structural behaviors (i.e. extension, flexure, torsion, etc). The safety ofbridge would be doubted without consideration of the cross-section warping and shearlag effect in design. Shear lag effect is not considered in the actual design but justdiscussed academically for the reason of the insufficient research in our country. Inthis paper, a shell finite element model of single-box and single-cell box-girder basedon the shell finite element method is proposed and a model test is carried out to verifythe shear lag as well as the nonlinear bearing behavior of curved box-girder further.The main content is as following: Considering the structural behaviors of curved box-girder and the analyticdemands of shear lag effect, 8-nodes plane shell element is used to build spatial finiteelement model and a corresponding spatial finite element analytic program isdeveloped by FORTRAN language. A typical example validates that the resultcalculated by the program is in well agreement with the example’s, which shows thatthe program is reliable and applied;Through analysis, the generant reason of shear lagphenomenon is tried to be explained further. In order to distinguish the nonuniformdistribution of direct stress on top plate caused by torsion and shear lag effect,suggestion has been brought forward on the definition of shear lag coefficient withconsideration of the nonuniform distribution of force on internal-external web platesof curved box girder. For the purpose of studying influence of prestress on shear lageffect, the property of prestress bar in the curved box-girder is analyzed based onspace vector theory and the influence of prestress on the shear lag of curved boxgirders was explored at elastic stage based on the equivalent load method;A separatedreinforced concrete finite element model is established by ANSYS, which is used toanalyze the non-linear characteristic of the test specimens;Potential problems ofexperiment and theory are analyzed based on the comparison between prestressconcrete model experimental results and academic results.Academic calculation and experimental investigation indicate that:(1) Shear lageffect is mainly caused by the non-uniform variation of longitudinal shear stress. (2)Shear lag coefficient will be reduced at the mid-span section of curved box-girder andincreased near the beam end. (3) The ANSYS non-linear finite element analysisresults is in well agreement with the test results, which proves that the method ofmodel building is feasible.更多还原