【作者】 李观宇；

【导师】 陈朝晖；

【作者基本信息】 重庆大学 ， 工程力学， 2010， 硕士

【摘要】 市政排水管道是城市防洪排涝、输送污水的设施,是城市基础设施的重要组成部分。本文以重庆市排水主干管A管线为研究背景,对滑坡等地质灾害作用下的排水管道埋地箱涵进行了受力分析,主要研究内容和结论如下:首先,介绍了现有滑坡推力的计算方法,利用传递系数法计算了A管线典型地段的滑坡推力。通过建立滑坡发生时埋地管道的受力模型,推导了考虑剪切变形影响的管道内力、变形方程。分析结果显示,剪切变形对跨越管道的纵向位移影响较大,对管线内力的影响则不明显。同时,地基土体对管道有明显的支撑作用,管道完全悬空时是受力最不利的工况。其次,以A管线典型管段的埋地箱涵为原型,制作了2根缩尺比例为1:5的钢筋混凝土箱梁进行单调静力加载试验。试验构件表现为剪切破坏,裂缝分布比较均匀,没有出现明显的临界斜裂缝。破坏形态经历了腹剪斜裂缝开展,弯曲裂缝出现,弯剪斜裂缝开展,斜压杆压溃阶段。混凝土开裂前,构件的剪切变形较小,主要以弯曲变形为主。斜裂缝开展到一定宽度后,构件的抗剪刚度急剧减小。构件底板配置了较多纵筋,达到最大极限承载力之后,挠度增长比较大,非突然破坏。试验结果表明,箍筋在混凝土开裂之后承担了较多的剪力,为主要的抗剪部件。底板纵筋在加载初期为线性增长,出现弯曲裂缝时纵筋应变骤增。纵筋应变受多种因素影响,只有部分区域呈现剪力滞效应。腹板纵筋应力沿高度分布情况表明,开裂之前截面应变基本符合平截面假定,开裂之后则不符合。最后,采用有限元软件ABAQUS中的损伤塑性模型,对试验梁进行了非线性有限元模拟。分析结果表明有限元模型较好地模拟了构件的破坏形态,对极限承载力的模拟效果也较好。但是有限元模型刚度偏大,分析全过程的挠度均小于试验测得的位移值。有限元分析结果表明底板纵筋应力符合正剪力滞现象,腹板纵筋应力沿高度分布则显示平截面假定成立。更多还原

【Abstract】 Sewerage pipes are important infrastructures of urban flood-proof and sewage transmission. It is necessary to analyze the mechanical behavior of drainage pipe in various working situations for the safe of the municipal sewerage pipeline system. On the background of Chongqing downtown sewerage system’s A pipeline project, the response of the buried box culvert to landslide were analyzed. The main work and conclusions were present as follows:Firstly, the current method of landslide thrust calculating was introduced. The landslide-thrust of typical part of A line by means of load transfer factor method was calculated. Mechanical model of buried pipe was created when landslide occurred, and then inner force and deformation equations, including shear effect, was obtained. The analyzed results showed that shear deformation had a tremendous influence to longitudinal displacement of spanning pipe, with a little effect of pipeline inner force. The soil of the foundation played an apparently bearing action to pipe. The least favorable situation was that the pipe was completely suspended.Secondly, prototyping with A pipeline typical buried box culvert, model beam was designed and statically tested in structural laboratory of Chongqing University. The crack distribution of test beam was uniform, and there was no critical declining crack in beam body. We could conclude that the failure mode of test beam was shear failure. About the mechanical process of the test beam, four stages could be characterized as web-shearing declining crack stage, flexural crack stage, flexure-shearing declining crack stage and diagonal rod squashing stage. The flexural deformation was main before the test beam cracked, while shear effect was less. The shear stiffness of the component sharply decreased after declining crack developed a wide certain. After the component reached its ultimate bearing capacity, the deflection was increasing a lot as a result of much reinforcement in bottom plate. On the whole, the test beam did not suddenly corrupt.The experimental results betrayed that the stirrups devoted much to shear capacity of the box girder. The longitudinal steel strain in bottom plate presented a linearly increasing process, but abruptly mutated when flexural crack occurred. Only in a small part was there shear lag effect because the longitudinal steel strain was influenced by many other factors. From the distribution principles of longitudinal bars, it was demonstrated that the test beam could not accord with plane cross-section assumption whether cracking or not.Finally, the test beam was modeled by damage-plastic model in the nonlinear finite-element software ABAQUS. The simulated results agreed well with the experimental data, especially for the failure mode of the box beam. However, all of the deflection in every sub-step was less than that in testing process owing to the larger stiffness of finite-element model. The finite-element results demonstrated that there was shear lag effect in longitudinal rebar in the bottom plate. The plane cross-section assumption was also satisfacted for the longitudinal steel in the web plate of the box beam.更多还原