【作者】 周亚栋；

【导师】 邵旭东；

【作者基本信息】 湖南大学 ， 桥梁与隧道工程， 2013， 博士

【摘要】 在传统预应力混凝土桥梁设计和施工过程中，提高梁的预应力度和减小梁的徐变上拱是一对不可调和的矛盾；高速铁路对桥梁结构安全性、线路平顺性提出了更高的要求，使得这一对矛盾在高速铁路桥梁中更加突出，如何控制预应力混凝土桥梁徐变上拱成为高速铁路桥梁的关键技术问题。本文提出把具有良好控制结构徐变上拱变形能力的二次预应力组合梁应用到高速铁路桥梁中，以结构设计为切入点，以更经济合理的方案解决高速铁路桥梁的关键技术问题，具有重要的学术意义和工程价值。在总结铁路预应力混凝土桥梁徐变上拱控制方法和二次预应力组合梁技术发展的基础上，本文对高速铁路二次预应力组合梁受力性能和设计方法进行了深入研究，主要开展了如下研究工作：（1）把二次预应力组合梁应用到高速铁路桥梁中，对相同条件下（结构尺寸、预应力筋配置、非预应力筋配置、施工方法、各类荷载值均相同）常规预应力混凝土梁和二次预应力组合梁进行了对比分析，主要分析两种结构的受力性能、变形性能和技术经济性，论证了二次预应力组合梁应用到高速铁路桥梁中的可行性和技术经济优势；（2）以跨径32m的有碴轨道简支箱梁为例，按相同条件制作常规预应力混凝土梁和二次预应力组合梁1︰3大比例试验模型梁，进行了两根模型梁从施工到静载破坏各阶段受力性能、变形性能的对比试验研究，主要研究了施工阶段正截面应力与上拱变形、裂缝的开展与分布规律、极限承载力、荷载—挠度曲线、荷载—应变曲线、水平结合面混凝土应变等；（3）进行了为期26个月的常规预应力混凝土梁和二次预应力组合梁1︰3大比例模型梁的徐变效应对比试验，采用四次幂函数曲线按拟合的方法，并考虑先浇梁长度指标β的影响，推导了更具有普遍意义的二次预应力组合梁徐变上拱变形的计算公式；（4）模拟高速铁路二次预应力组合梁水平结合面的受力状态，考虑结合面抗剪钢筋配筋率、两期混凝土龄期差、结合面应力差三个因素，采用正交方法制作推出试件，进行了45个推出试件结合面静载抗剪性能试验和7个推出试件结合面疲劳抗剪性能试验，研究分析了结合面静载抗剪性能和疲劳抗剪性能，提出了结合面抗剪强度的计算方法；（5）研究分析二次预应力组合梁的结构特点，提出了二次预应力混凝土的两种新概念，第一种概念是：二次施加预应力的目的是把梁跨中段底部混凝土变为抗拉强度高的弹性材料，第二种概念是：二次施加预应力的目的是提高高强度钢筋和混凝土共同工作的效率；（6）提出了二次预应力组合梁先浇梁三个设计参数的概念，即先浇梁高度指标α、先浇梁长度指标β和先浇梁一期预应力筋指标γ；提出了一套二次预应力组合梁实用设计方法及相应的计算公式，主要包括：消压弯矩、开裂弯矩的计算；截面尺寸的估算；一期预应力筋面积、二期预应力筋面积的估算；先浇梁强度和稳定性验算；正截面强度、斜截面抗弯强度、斜截面抗剪强度、水平结合面静载与疲劳抗剪强度的计算；预应力损失的计算；正截面抗裂性的验算；先浇梁锚固区抗弯强度和抗裂性的验算；徐变上拱的计算；截面开裂后挠度的计算等。更多还原

【Abstract】 To improve the prestress degree and to reduce the creep camber of bridgesimultaneously poses an irreconcilable contradiction in the design and construction ofconventional prestressed concrete bridge. This issue becomes more serious inhigh-speed railway bridges, as these bridges have more strict requirement in structuresafety and track regularity, resulting in a critical technical problem to control thecreep camber in the high-speed railway prestressed concrete bridges. In thisdissertation, the twice prestressed composite beam is proposed to be applied to thehigh-speed railway bridges, in which the creep-induced deformation can be wellcontrolled. The irreconcilable contradiction can be solved on the basis of structuraldesign, which is of significant academic value and potential application inengineering practice.Based on comprehensive literature review of the controlling methods for creepcamber in prestressed concrete railway bridges and technical development of twiceprestressed composite beams, the mechanical performance and design method of thetwice prestressed composite beams on high-speed railway were studied in thedissertation, and the main accomplishments are as follows:1) For the application of the high-speed railway bridges, theoretical analysis wasperformed to compare the twice prestressed composite beam with the conventionalprestressed concrete beam under the same conditions, including the structuraldimension, the configuration of prestressed steel bars, the passive reinforcement ratio,the construction method, and the load conditions, etc. The analysis was mainlyfocused on the stress and deformation performance in these two types of beams, andthe technological economy as well. The results revealed the feasibility andeconomical advantages when applying the twice prestressed composite beam to thehigh-speed railway bridge.2) Taking a32-m simply supported box girder ballastless track bridge as anexample, two large-scale model beams in the scale of1:3were constructed forexperiment under the same conditions. One beam was the conventional prestressedconcrete beam, and the other was the twice prestressed composite beam. The twobeams were loaded to compare their mechanical and deformation performance fromits construction stage to its damage stage, including the development and distribution of cracks, the normal stress and the camber of the beams in the construction stage, theultimate bearing capacity, the load-deflection curves, the load-strain curves and thestrain at horizontal interface in the composite beam.3) Two1:3large scale model beams, namely, the prestressed concrete modelbeam and twice prestressed composite model beam, were loaded with static loads for26months to investigate the creep effect, adopting the curve fitting method with fourtimes power function, a formula with more universal meaning to calculate the creepcamber in the twice prestressed composite beam were deduced, considering theinfluence of precast beam length index β.4) To investigate the mechanical behavior at the interface of the twiceprestressed composite beam,52push-out specimens were constructed adoptingorthogonal method.45specimens were for static load test and the remaining7forfatigue load. The construction of the52specimens considered the factors relating tointerface characteristics, including the shear reinforcement ratio, concrete agedifference and stress difference. The method of calculating interface shear strengthwas presented according to push-out test results.5) Based on analysis of structure characteristics of the twice prestressedcomposite beams, two new conceptions with respect to the twice prestressed concretewere put forward. The first conception states that the purpose of the twice prestressedconcrete is to transform the concrete at the bottom of middle span region into theelastic material with high tensile strength. The second conception proposes that thepurpose of twice prestressed concrete is to improve the co-work efficiency of highstrength steel and high strength concrete.6) The concept of three design parameters for the precast beam in the twiceprestressed composite beam was presented, namely, the precast beam height index α,the precast beam length index β, and the first term prestress steel index of theprecast beam γ. A serial design method and corresponding calculation formulae ofthe twice prestressed composite beam were proposed, covering: decompressionmoment and cracking bending moment, estimation of cross section dimensions, areaof the first and the second term prestress steel, strength and stability of the precastbeam, bending strength in normal cross-section or inclined-section and shear bearingcapacity in inclined-section, static and fatigue shear strength at horizontal interface ofthe twice prestressed composite beam, prestress loss, crack resistance performance innormal section, bending strength and crack resistance performance at anchorageregion in the first term prestress steel, creep camber, and post-crack deflection, etc.更多还原