【作者】 李学斌；

【导师】 杨梦蛟；

【作者基本信息】 铁道部科学研究院 ， 桥梁与隧道工程， 2003， 硕士

【摘要】 预制节段拼装施工法是近四十年内才发展起来的施工方法。预制节段拼装原理是借助预应力束施加于混凝土节段上的压力，使得节段间接触面紧密贴合，形成整体结构共同承担荷载。预制节段拼装施工一般可采用悬臂拼装和逐跨拼装。预制节段拼装技术的主要优点有：(1)梁体分段预制，施工质量好，风险小；上部结构几何线形容易控制。(2)施工速度快，工期短；上部结构节段预制可与下部结构施工同时进行。(3)施工机械化程度高，特别适合于长大桥梁的快速施工。(4)节段养护时间长，加载龄期晚，成桥后梁体徐变上拱和预应力长期损失小。(5)对桥址周围自然生态环境破坏小；对桥下现有交通及周边社区环境影响小。预制节段拼装体外预应力结构紧密结合着现代施工工艺和预应力的发展方向。预制节段拼装作为一种可靠、经济、实用的施工方法，目前已得到世界各国的普遍认可，而且在实际工程中得到广泛应用。体外预应力技术与预制节段拼装施工方法的结合应用是解决桥梁施工质量和施工速度矛盾的较好途径。预制节段拼装体外预应力结构在国外经过二十多年的发展，施工技术已较成熟，但在国内该技术的应用尚处于起步阶段。近年来在我国公路和市政桥梁领域已经开始应用这一技术，但在铁路桥领域该技术还尚未进行 铁道科学研究院硕士学位论文较全面的研究，因此有必要针对我国铁路建设的需要，对高速铁路节段拼装体外预应力桥梁受力特性和破坏形态进行较为全面的分析研究。本文依托铁道部“新建铁路节段式预应力混凝土箱梁关键技术的试验研究”科研项目，结合京沪高速铁路桥梁初步设计，对预制节段拼装体外预应力混凝土箱梁弯曲受力特性进行了分析研究。 本研究应用ANSYS有限元程序建立预制节段拼装体外预应力梁的三维有限元模型。针对预制节段干接缝拼装梁存在接缝的特点，采用接触单元模拟接缝间的相互作用，解决了预制节段拼装梁建模的关键问题，并在计算模型中考虑了混凝土材料非线性和结构几何非线性的影响。通过对B．GRabbat、K．S。Wlat试验模型和法国CEBTP机构试验模型的有限元分析比较，验证了本研究所采用的计算模型能够较准确地模拟节段梁的弯曲受力特性。 以跨度39．lin简支箱梁和2 X 40m连续箱梁为例，本文较全面地分析了预制节段拼装体外预应力混凝土箱梁全过程受力特性和正截面弯曲破坏形态；研究了不同预应力配筋面积和预应力筋重心高度对预制节段拼装体外预应力简支梁极限承载力和延性的影响，以及体外预应力节段简支梁与体外预应力、体内有粘结预应力整体简支梁极限承载力和受力特性的差异。研究结果表明：在接缝消压之前，预制节段拼装体外预应力梁受力特性与整体梁相同，梁体挠度为线性变化；在接缝消压以后，预制节段拼装梁接缝开始张开，受接缝截面转动的影响，梁体挠度转为非线性变化。随着荷载的增加，接缝开展高度和宽度、梁体挠度、截面压应变都呈现较快增加趋势；干接缝节段梁的开裂仅出现在接缝位置，梁体最终以接缝截面受压区混凝土出现局部压溃而破坏；在极限状态，预制节段拼装梁体外束应力增量不大，预应力束配筋面积对其影响较小；体外束偏心距变化小于 2 铁道科学研究院硕士学位论文1％，对抗弯极限承载力影响较小。节段梁在承载力极限状态竖向位移与相应弹性阶段竖向位移之比大于2，仍具有较好的延性；当满足现行《桥规》极限承载力设计要求时，预制节段拼装体外预应力梁预压应力水平相对较高。体外配束节段梁与体外配束及体内有粘结配束整体梁相比，在相同预应力束配筋量和预压应力水平下，极限承载力状态体外配束节段梁竖向挠度和预应力束应力增量均低于后二者，极限承载力分别为后二者的钻％和76％；在相同偏心距、有效预应力、极限承载力下，体外配束节段梁预应力束配筋面积分别为体外配束和体内有粘结配束整体梁的l．08＄01．32。两跨节段拼装体外预应力连续梁破坏时梁体挠度和预应力束极限应力增量均较小。对于同等跨度的节段连续梁与节段简支梁，设计时采用连续梁可以降低梁高，改善使用状态混凝土预压应力水平和梁体裂后性能。 本研究为体外预应力预制节段拼装梁的理论分析提供了有效的计算方法，为铁路预制节段拼装体外预应力混凝土箱梁设计提供了有参考价值的结论。在体外束配置适当的情况下，预制节段拼装简支梁和连续梁在我国高速铁路桥梁上应用是可行的。当前我国高速公路桥梁、市政桥梁和城市轻轨桥梁发展较快，预制节段拼装体外预应力结构在这些工程中具有广阔的应用前景。预制节段拼装施工和体外预应力技术在长大桥梁中的应用具有其它施工方法不可比拟的优势，定会在我国桥梁建设中发挥巨大的作用。更多还原

【Abstract】 The method of precast segmental construction began to evolve 40 years ago. The principle of precast segmental construction lies in that concrete segments are assembled as a whole structure to bear load through pressure acted on the segments by post-tensioning tendons. Precast segmental construction may adopt two methods generally: balanced cantilever construction and span-by-span construction.The principal advantages of precast segmental construction may be summarized as follows:1. As the girders are fabricated segmentally, there are reliable qualities and small ventures during superstructure construction. Furthermore, geometrical sizes of superstructures are easier to perform.2. The prefabrication of superstructure segments can be processed while the substructure is under construction. So it will speed up the erection of bridges and shorten the time of construction.3. The construction mechanization is relatively high, so precast segmental construction is superior to other methods of construction in the long or long-span bridges.4. As a result of the maturity of the concrete and the application of prestress after long-time maintenance, effects of concrete creep and long-term loss of prestress can be minimized.5. Precast segmental construction can minimize the impact on natural environment and residential community. Interference with existing traffic under bridges during construction is significantly reduced.Precast segmental structure with external tendons (PSBGET) closely accords with the development of prestressing technique and modern construction technology. As a safe, economic and practical construction method, it has been widely accepted and utilized in the bridge engineering all over the world. The combination of the external prestressing technique and precast segmental construction technology in the engineering is a good way to settle the conflict between the quality and the speed of bridge construction.As PSBGET has evolved remarkably in the past 20 years, the construction technology of PSBGET is relatively mature in other countries now. But in our country, its utilization is still of initial stage. In the last few years, it has been used in the field of highway bridges and civic bridges. However, in the field of railroad bridges, the comprehensive studies of this technology have not begun. So it’s necessary to analyze and study the mechanical characteristics and failure states of PSBGET in high-speed railways, with the requirements of railroading in our country taken into consideration. Based on the research project of "experimental study on the key techniques of PSBGET in the railway bridges" and the preliminary designs of Jing-hu high-speed railway bridges, mechanical characteristics of PSBGET are analyzed and studied in this thesis.The finite element models of PSBGET are established in the thesis by utilizing finite element software, ANSYS. Owing to the joints in the precastsegmental box girders, the key problem is how to simulate the interactions between the joints. In the thesis, 3D finite element, models (FEM) of the precast segmental box girders are established with contact elements, which may simulate the interactions between the joints. The influences of material nonlinearity of concrete and geometric nonlinearity of structure are also taken into account in the computed models. 3D-FEM analyses of B.GRabbat and K.Sowlat’s experimental model and CEBTP (France) experimental model have proved that the computed models can actually reflect the mechanical characteristics of PSBGET.Based on the simulating results of simply-supported box girders (39.1m)and continuous box girders (2 X 40m), the paper emphatically analyzes the full mechanical characteristics of PSBGET and the bend failure states of the right section. The influence of different areas and eccentricities of external tendons on ultimate bearing capacity and ductility is studied in detail. The differences of ultimate bearing capacity and the mechanical characteristics between the se更多还原