裂纹损伤对大跨径预应力砼连续箱梁桥刚度及承载力的影响研究

发布时间：2018-09-17 16:08

【摘要】：随着我国交通事业的不断发展，大跨径预应力混凝土连续箱梁桥凭借其施工方法灵活、刚度大、跨度大、结构受力性能好等优点在工程界得到了广泛应用。但是调查研究发现，有相当数量的这种桥梁在运营过程中，箱梁截面出现了部位各异、程度各异的裂缝。裂缝的存在将会使桥梁结构的安全性与耐久性受到影响，因此，必须进行相应的加固维修。然而，桥梁数目众多，不可能逐一进行加固修补，因此，就需要科学的判断开裂结构的实际状态，以区分轻重缓急，为制定合适的维修、改造方案提供依据。现如今，对大跨径预应力箱梁桥开裂后状况的研究还很少，如何对开裂结构的实际工作状态进行准确的判断一直未能解决。本文以黄延高速洛河大桥为依托，从箱梁产生的主要病害裂缝（跨中正弯矩区段底板横向裂缝）入手，对开裂前后结构进行静力、动力分析，得到不同开裂状态下结构的刚度、承载能力及动力性能（频率）的变化规律。首先，本文对箱梁裂缝的产生原理、形成因素及裂缝分类进行了理论分析，发现裂缝的产生具有不可避免性，，裂缝的研究具有实际意义。之后，本文依据统计学原理建立了底板横向裂缝的特征统计参数，旨在将实际存在的裂缝转化为统计意义下的平均裂缝，通过在梁段上创造既有裂缝的方法进行模拟研究。其次，论文还对有限元分析所需的单元、本构关系、裂缝模型、混凝土破坏准则等进行了系统研究，为模型的建立及求解计算提供理论依据。最后，论文根据实桥设计资料建立开裂前后结构的空间实体模型，分析了纵向预应力损失、裂缝失效宽度、裂缝开裂高度、裂缝条数等不同裂缝参数改变时，结构的应力、挠度、频率的变化规律，获得不同开裂状态下结构的刚度、承载能力及频率的折减系数。分析结果表明：（1）纵向预应力损失对结构墩顶处的挠度影响不大，对结构跨中处的挠度影响较大；（2）纵向预应力损失对结构墩顶处和跨中处的压应力均有较大影响；（3）底板横向裂缝的单元失效宽度对结构影响不大；（4）裂缝高度对结构有一定影响，但开裂高度不大时影响微小，且开裂到一定高度后又会逐渐趋于稳定；（5）裂缝条数对结构影响较大。
[Abstract]:With the continuous development of transportation in our country, long-span prestressed concrete continuous box girder bridge has been widely used in engineering field by virtue of its flexible construction method, large stiffness, large span and good mechanical performance. But the investigation found that a considerable number of such bridges in the operation process, box girder cross-section of different parts, varying degrees of cracks. The existence of cracks will affect the safety and durability of bridge structure. However, there are so many bridges that it is impossible to reinforce and repair them one by one. Therefore, it is necessary to scientifically judge the actual state of the cracked structure in order to distinguish the priority and order of priority, and to provide the basis for the formulation of appropriate maintenance and renovation schemes. Nowadays, there are few researches on the post-cracking condition of long-span prestressed box girder bridge, how to accurately judge the actual working state of the cracked structure has not been solved. Based on the Luohe Bridge of Huangyan High Speed, this paper starts with the main damage cracks (transverse cracks in the bottom slab of the section of mid-bending moment), analyzes the structure before and after cracking, and obtains the stiffness of the structure under different cracking conditions. The variation of bearing capacity and dynamic performance (frequency). Firstly, this paper makes a theoretical analysis of the generation principle, formation factors and classification of cracks in box girder. It is found that the occurrence of cracks is inevitable and the study of cracks is of practical significance. Then, based on the statistical principle, this paper establishes the characteristic statistical parameters of the transverse cracks in the bottom plate, aiming at transforming the actual existing cracks into the average cracks in the statistical sense, and simulating the method of creating the existing cracks on the beam section. Secondly, the element, constitutive relation, crack model and concrete failure criterion needed for finite element analysis are systematically studied in this paper, which provides the theoretical basis for the establishment of the model and the calculation of its solution. Finally, according to the design data of the real bridge, the spatial solid model of the structure before and after cracking is established, and the stress of the structure is analyzed when the longitudinal prestress loss, crack failure width, crack height, crack bar number and other crack parameters change. The stiffness, bearing capacity and frequency reduction coefficient of the structure under different cracking conditions are obtained by the variation of deflection and frequency. The results show that: (1) the longitudinal prestress loss has little effect on the deflection at the top of the pier, but has a great effect on the deflection at the middle of the span, (2) the loss of longitudinal prestress has a great effect on the compressive stress at the top of the pier and at the middle of the span. (3) the failure width of the transverse crack of the bottom plate has little effect on the structure, (4) the crack height has a certain influence on the structure, but the crack height has little effect on the structure, and the crack will gradually become stable after cracking to a certain height. (5) the number of cracks has great influence on the structure.
【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

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