体外预应力加固混凝土T梁及箱梁的试验研究

发布时间：2018-01-24 03:52

本文关键词： 体外预应力混凝土梁全过程分析受弯性能延性应力增量　出处：《北京交通大学》2016年硕士论文　论文类型：学位论文

【摘要】：体外预应力加固是一种主动的加固方式,能够显著提高结构的承载力。由于具备施工快捷、维护管理方便、自重轻等优点,体外预应力技术被广泛应用于桥梁的新建和加固。本文基于6根体外预应力加固混凝土梁的试验对体外预应力梁的受力性能展开相关研究。本文的研究工作主要包括以下四个部分：第一,对3根体外预应力加固混凝土T梁和3根体外预应力加固混凝土箱梁进行全过程加载试验,通过分析试验梁的应变、挠度、裂缝发展等试验数据和现象,研究了不同加固方式和不同的体外预应力筋有效高度对梁加固效果和受力行为的影响。通过试验发现,设置体外预应力筋的试验梁抗弯承载力提高了50%以上,卸载加固可以使原有裂缝完全闭合,而带载加固时原有宽度较大的裂缝的宽度减小,原有宽度较小的裂缝闭合。增大体外预应力筋的有效高度可以提高梁的抗弯承载力。第二,通过合理简化计算模型,以弯矩-曲率分析为基础,结合共轭梁法,建立体外预应力混凝土梁弯曲性能的全过程分析方法,并利用Matlab编制了计算程序。通过试验值与计算值的比较,证明本文所建立的全过程分析方法的计算精度较高。在此基础上,对跨高比、混凝土强度、普通钢筋及预应力筋等参数对梁受弯性能的影响进行具体分析。第三,以位移延性系数为指标,分析了试验梁的延性特征,并对混凝土强度、受压区普通钢筋指标、受拉区普通钢筋指标、部分预应力比率、体外预应力筋有效高度等几个影响梁延性的因素做了参数分析。通过研究发现,与未加固梁相比,加固梁的位移延性系数减小,带载加固和卸载加固对梁最终的延性损失影响较小,增大体外预应力筋的有效高度可以在减小延性损失的情况下显著提高梁的抗弯承载能力。第四,研究了体外预应力筋在加载过程中的应力变化情况,以及体外筋对体内筋应力的影响,并建议了加固设计时预应力筋极限应力的计算公式。针对公路桥梁体外预应力加固,推导了加固时所需的体外预应力筋用量的上限值。在此基础上,分析了跨高比、混凝土强度等因素对预应力筋应力增量的影响。本文的研究成果有助于加深对体外预应力混凝土结构的理解,也为体外预应力混凝土桥梁的新建和加固设计提供了技术支持。
[Abstract]:External prestressed reinforcement is an active reinforcement method, which can significantly improve the bearing capacity of the structure. Because of the advantages of quick construction, convenient maintenance and management, light weight and so on. External prestressing technology is widely used in the construction and reinforcement of bridges. Based on the experimental results of 6 externally prestressed concrete beams, the mechanical behavior of externally prestressed beams is studied in this paper. The main work of this paper is to study the behavior of externally prestressed concrete beams. It consists of the following four parts:. Number one. Three concrete T-beams strengthened by external prestressing and three concrete box girders strengthened by external prestressing were tested in the whole process, and the experimental data and phenomena of strain, deflection and crack development of the test beams were analyzed. The effects of different reinforcement methods and different effective heights of external prestressed tendons on the strengthening effect and mechanical behavior of beams are studied. The flexural bearing capacity of the test beam with external prestressed tendons is increased by more than 50%, and the original crack can be completely closed by unloading and strengthening, while the width of the crack with the larger width is reduced when the load is strengthened. The original crack closure with small width. Increasing the effective height of external prestressed tendons can improve the flexural capacity of beams. Second, through reasonable simplification of the calculation model, based on the moment curvature analysis, combined with conjugate beam method. The whole process analysis method of the bending behavior of externally prestressed concrete beams is established, and the calculation program is compiled by using Matlab. The comparison between the experimental values and the calculated values is carried out. It is proved that the calculation accuracy of the whole process analysis method established in this paper is high. On this basis, the ratio of span to height, the concrete strength is obtained. The influence of the parameters such as common reinforcement and prestressed tendons on the flexural behavior of the beam is analyzed in detail. Thirdly, the ductility characteristics of the test beam are analyzed with the displacement ductility coefficient as the index, and the concrete strength is analyzed. Several factors affecting the ductility of beam are analyzed, such as the index of common steel bar in compression zone, the index of ordinary steel bar in tension area, the ratio of partial prestressing force and the effective height of external prestressing tendons. Compared with the unstrengthened beam, the displacement ductility coefficient of the strengthened beam decreases, and the ultimate ductility loss of the beam is less affected by the consolidation with load and the unloading reinforcement. Increasing the effective height of external prestressed tendons can significantly improve the flexural bearing capacity of beams under the condition of reducing ductility loss. 4th. The stress changes of external prestressed tendons during loading are studied. The influence of external tendons on the stress of internal tendons and the calculation formula of ultimate stress of prestressed tendons in reinforcement design are suggested. The upper limit of the amount of external prestressing tendons needed for reinforcement is deduced. Based on this, the ratio of span to height is analyzed. The effect of concrete strength and other factors on stress increment of prestressed tendons. The research results in this paper are helpful to deepen the understanding of external prestressed concrete structures. It also provides technical support for the construction and reinforcement design of externally prestressed concrete bridges.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U446;U445.72

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