体外预应力加固铁路盖板涵力学性能研究

发布时间：2018-03-24 11:43

本文选题：体外预应力筋加固　切入点：跨中挠度　出处：《兰州交通大学》2015年硕士论文

【摘要】：我国20世纪70-90年代初修建的盖板涵大部分在使用。虽然结构设计荷载较低,但盖板涵的各种病害日益加重,已经不能满足日益增长的重载化要求,对既有盖板涵结构进行加固实现提载凸显重要。作为一种简便的加固方式—体外预应力加固,对提高钢筋混凝土梁整体承载能力不足等问题非常有效,故在工程界被广泛地使用,并在施工中得到了不断的创新。目前,体外预应力的研究大多是参考无粘结预应力的研究理论,本文也借鉴已有的研究理论,以体外预应力筋加固大秦铁路盖板涵静载试验为研究背景,基于体外预应力筋应力增量与梁体跨中挠度及混凝土压应变的相关性,针对盖板涵结构体外预应力筋加固的局限性,提出了梁底直线体外预应力筋加固盖板涵结构计算模型,系统地对用截面应变和挠度表示的体外预应力筋应力增量作了分析,相关工作如下:(1)介绍了国内外对体外预应力结构的研究现状以及盖板涵常见的加固方法,各自的加固计算原理进行了讨论,并比较了各方法的优缺点。(2)利用梁体变形前后的几何关系,推导了铁路运营阶段体外预应力加固盖板涵在均布荷载、三分点荷载、集中荷载作用下的应力增量的统一表达式。并与截面剪力、弯矩平衡关系式迭代计算,考虑反弯矩对应力增量的影响,最终得到应力增量的数值解。并进一步对影响加固效果的各参数敏感性做了分析。(3)对盖板涵建立有限元MIDAS/FEA实体模型进行结构内力分析。模型值与理论值吻合较好,可以满足本文计算要求。(4)根据相似原理制作了1:1大秦铁路盖板涵体外预应力加固模型,在试验室大厅进行了正常使用阶段下静载试验。试验中主要测量了挠度、钢筋应变、混凝土应变、体外筋应变,跟加固前比较,施加不同有效预应力,混凝土压应变、挠度、钢筋应变、体外筋应力增量减少幅度较大,加固效果明显。通过与试验数据比较,本文的理论值与试验值吻合较好。对于梁高较小的盖板涵来讲,近似取值相对误差较大。因此,本文体外预应力筋应力增量计算方法仅对于盖板涵采用梁底直线布筋且无转向块的体外预应力加固具有一定的通用性,建议在后续的研究中继续改善。
[Abstract]:Most of the slab culverts built in China in the early 1970s and 1990s are in use. Although the structural design load is relatively low, the various diseases of the cover culverts are becoming more and more serious and can no longer meet the increasing requirements of heavy loading. It is very important to strengthen the existing slab culvert structure and realize the lifting load. As a simple way of strengthening, external prestressing reinforcement is very effective to improve the overall bearing capacity of reinforced concrete beam. Therefore, it is widely used in engineering field, and has been innovated continuously in construction. At present, the research of external prestressing is mostly referring to the research theory of unbonded prestressing, and this paper also draws lessons from existing research theories. Based on the static load test of the Da-Qin railway slab culvert strengthened by external prestressed tendons, based on the correlation between the stress increment of external prestressed tendons and the mid-span deflection of beam and the compressive strain of concrete, the limitations of external prestressing tendons reinforcement of slab culvert structures are pointed out. In this paper, the calculation model of the slab culvert structure strengthened by the straight external prestressed tendons at the bottom of the beam is presented. The stress increment of the external prestressed tendons expressed by the cross section strain and deflection is analyzed systematically. The related work is as follows: (1) the research status of external prestressed structures at home and abroad as well as the common reinforcement methods of slab culverts are introduced, and their strengthening calculation principles are discussed. The advantages and disadvantages of each method are compared. (2) based on the geometric relationship before and after the beam deformation, the paper deduces the load of uniform distribution and three-point load strengthened by external prestressing in railway operation stage. The unified expression of stress increment under concentrated load is calculated iteratively with the equilibrium relation of cross-section shear force and moment, and the effect of reverse moment on stress increment is considered. Finally, the numerical solution of the stress increment is obtained. Furthermore, the sensitivity of the parameters affecting the reinforcement effect is analyzed. The structural internal force analysis of the finite element MIDAS/FEA solid model of the cover plate culvert is carried out. The model value is in good agreement with the theoretical value. According to the similarity principle, the external prestressing reinforcement model of the cover culvert of the 1:1 Da-Qin railway was made, and the static load test was carried out in the laboratory hall during the normal service stage. The deflection and the strain of the steel bar were mainly measured in the test. The strain of concrete, the strain of external reinforcement, compared with that before reinforcement, different effective prestress, compressive strain of concrete, deflection, strain of reinforcing bar, stress increment of external reinforcement are greatly reduced, and the effect of reinforcement is obvious. The theoretical values in this paper are in good agreement with the experimental values. For the slab culverts with small beam height, the approximate relative error is larger. In this paper, the calculation method of stress increment of external prestressing tendons is universal only for the reinforcement of external prestressing without steering block, which is directly distributed at the bottom of beam, and it is suggested that it should be further improved in the following research.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U445.72

【共引文献】