基于弹塑性损伤模型的PC箱梁腹板反向裂缝形成机理及分析

发布时间：2018-06-17 12:18

本文选题：PC箱梁桥 + 反向裂缝　；参考：《长安大学》2014年硕士论文

【摘要】：箱形梁由于其良好的结构性能，在PC梁桥中应用广泛。但是该类桥梁在悬臂施工中箱梁腹板经常会出现与常规受剪裂缝走向垂直的斜裂缝——反向斜裂缝。目前工程界已公认此裂缝会影响桥梁整体安全性、实用性及耐久性，但是截至目前，技术人员对该类裂缝的形成机理，以及如何防范还没有给出一个明确的答案。因此本文旨在开展腹板反向斜裂缝的研究，寻找其形成原因，同时为新建桥梁防止该类病害的发生提供改进建议。本文以某连续刚构桥为工程背景，运用大型有限元计算软件ABAQUS分析了悬臂施工连续刚构箱梁桥腹板反向斜裂缝产生的原因，主要内容和结论结论如下：（1）分析给出了考虑竖向预应力、纵向预应力、剪力滞效应等因素下的施工阶段箱梁的应力的计算公式。（2）借助ABAQUS软件计算各种工况下腹板沿预应力方向预应力筋附近混凝土的主拉应力，并分析了造成腹板方向开裂的原因，对比分析了考虑预应力管道和不考虑预应力管道应力分布的差异。（3）在对预应力混凝土箱梁桥腹板反向斜裂缝影响因素研究的基础上，分别从箱梁桥的设计、施工、维修等层面提出了应对措施和建议。（4）张拉竖向预应力筋对腹板受力有利，因此张拉完纵向预应力筋后应及时张拉竖向预应力。（5）考虑预应力管道后腹板主拉应力明显大于不考虑管道的情况，因此在计算中应该考虑预应力孔道的影响。（6）造成腹板反向斜裂缝的主要原因是张拉腹板纵向预应力时锚固端应力集中和竖弯处径向力过大导致主拉应力超限。此外，张拉时机提前，，混凝土早期龄期未达到设计值也是一个不容忽视的原因。
[Abstract]:Box beam is widely used in PC beam bridge because of its good structure performance. However, in the cantilever construction of this kind of bridge, the box girder web plate often appears the oblique crack-reverse oblique crack which is perpendicular to the conventional shear crack. At present, it has been recognized that the crack will affect the overall safety, practicability and durability of the bridge. However, up to now, the technicians have not given a clear answer to the formation mechanism of this kind of crack and how to prevent it. Therefore, the purpose of this paper is to study the reverse oblique cracks of web plates, to find out the causes of the cracks, and to provide suggestions for the new bridges to prevent the occurrence of this kind of diseases. Taking a continuous rigid frame bridge as the engineering background, this paper analyzes the causes of the reverse oblique cracks in the web of the cantilever construction continuous rigid frame box girder bridge by using the large scale finite element calculation software Abaqus. The main contents and conclusions are as follows: (1) the vertical prestress and longitudinal prestress are considered. Calculation formula of box girder stress in construction stage under shear lag effect and other factors. (2) the main tensile stress of concrete near prestressed tendons in different working conditions is calculated by Abaqus software. The causes of the cracking in the web direction are also analyzed. This paper compares and analyzes the difference of stress distribution between prestressed pipe and non-prestressed pipe. On the basis of the research on the factors affecting the reverse oblique crack of web of prestressed concrete box girder bridge, the design and construction of box girder bridge are carried out respectively. At the maintenance and other levels, the countermeasures and suggestions are put forward. (4) the tension of vertical prestressed tendons is favorable to the web. Therefore, when the longitudinal prestressed tendons are finished, the vertical prestress should be tensioned in time. (5) the main tensile stress of the web plate after the consideration of the prestressed pipe is obviously greater than that without considering the pipeline. Therefore, the influence of prestress channels should be taken into account in the calculation. The main reason for the reverse oblique cracks of web plate is the stress concentration at the anchoring end and the excessive radial force at the vertical bend, which leads to the over-limit of the main tensile stress during the longitudinal prestressing of the web tensioning plate. In addition, the early tensioning time and the early age of concrete not reaching the design value are also a reason that can not be ignored.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U448.213;U441.6

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