【作者】 孙淑红；

【导师】 顾安邦；

【作者基本信息】 重庆交通大学 ， 桥梁与隧道工程， 2012， 博士

【摘要】 部分斜拉桥是“索辅梁”桥设计理念的一种体现。“索辅梁”桥的设计理念决定了这种新兴的桥梁结构体系具有构造设计方面的灵活性和技术经济方面的优越性。在梁式桥和斜拉桥之间的跨度范围内(100m-300m),部分斜拉桥无论在城市、还是山区、平原,都具有很强的适应性,并且对于刚度要求较高的轨道桥梁同样具有很强的竞争力。我国继芜湖长江大桥、福建漳州战备大桥之后,已经修建了几十座中等跨径的PC主梁部分斜拉桥,其中大宽度的PC箱梁已成为部分斜拉桥主梁的主要结构形式。而在重庆等地相继修建的几座外倾索面部分斜拉桥(例如主跨250m的重庆嘉悦大桥等),不仅整体结构在外型上新颖美观,其PC主梁更具有鲜明的技术特色。目前PC主梁部分斜拉桥的建设中,仍然有诸多技术问题需要进一步深入研究。例如：合理拉索倾角、无索区长度、主梁刚度、体内外预应力索的协调,以及PC宽箱主梁的空间受力性能等。本文以一座外倾索面的部分斜拉桥为工程背景,系统开展了部分斜拉桥概念设计阶段中的力学估算问题研究,深入地进行了影响部分斜拉桥整体结构性能的主要立面结构设计参数研究,以及长悬臂PC宽箱主梁的空间受力性能研究；并在理论研究的同时,开展了部分斜拉桥索梁锚固结构的1：3缩尺主梁节段模型试验研究。主要研究内容如下：1.部分斜拉桥概念设计阶段的估算公式在现有部分斜拉桥界定方法研究成果的基础上,结合部分斜拉桥“索辅梁”桥的本质特点,就桥梁概念设计中几个总体设计参数的确定原则,以及主梁的关键设计参数进行了系统的阐述；推导了梁、索的恒活载内力近似计算公式。2.重要结构设计参数的研究根据概念设计阶段的研究成果,进行了部分斜拉桥各种结构参数的重要性分析：对主梁刚度、无索区段长度、拉索初张力等几个重要参数对部分斜拉桥整体结构受力性能的影响进行了对比计算分析。建议部分斜拉桥结构参数的优化可以根据计算结果,按照不同的优化目标(例如：拉索活载应力变幅较小、预应力钢束效率提高等)来区别对待。研究成果对于明确部分斜拉桥的重要结构参数,进一步发挥部分斜拉桥的优势具有参考意义。3.外倾式双索面及拉索倾角对PC宽箱主梁的空间应力分布影响结合重庆嘉悦大桥的结构技术特点,进行了外倾索面PC箱形主梁部分斜拉桥整体空间结构的悬臂施工全过程仿真分析,得到其长悬臂PC宽箱主梁的空间主应力分布状态以及变化规律;并对特殊的索梁锚固结构建立更为精细的空间有限元模型,掌握了混凝土索梁锚固结构的应力传递情况和其在最不利施工阶段的力学行为。根据研究成果提出：长悬臂的PC宽箱薄壁结构设计中,构件的主应力成为控制设计的主要因素;在纵向、横向预应力都无法企及的区域,应采用优化、加强普通钢筋布置的办法来保证结构的安全性。4.部分斜拉桥长悬臂PC宽箱主梁顶板的剪力滞效应对比了各种剪力滞效应研究方法的适用性；利用空间有限元方法,研究了外倾索面部分斜拉桥的长悬臂PC宽箱主梁在全荷载作用(自重、预应力、拉索力、挂篮、砼时效、温度等)下,在悬臂施工全过程中,不同部位箱梁顶板的剪力滞效应。得到结论：受到拉索锚固结构、塔梁联结边界条件、挂篮力等的影响,在悬臂施工过程中长悬臂PC宽箱主梁的剪力滞效应十分突出,且正负剪力滞效应都存在；成桥后各区段主梁顶板的剪力滞系数均值大于1.0；同时还研究了拉索水平倾角变化时,索力轴向分力在纵向的传递规律的变化情况。5.索梁锚固结构主梁节段模型试验研究为验证拉索的混凝土锚固区在千吨级索力下的安全性,开展了主梁一节段1：3缩尺节段试验模型。根据空间计算结果,进行测点的定位；测试在不同拉索索力下,PC箱梁悬臂翼缘板以及锚固块处各测点的应力与变形,研究混凝土锚固块的应力分布情况,通过实测数据与空间有限元计算结果的对比分析,对拉索锚固区的优化设计提出合理建议。6.考虑预应力影响的部分斜拉桥PC主梁的索力优化简述索力优化的内容和方法,综合比较了以主梁截面的应力状态为条件,进行索力和预应力设计耦合优化的几种方法的特点。提出前进分析法是比较适合部分斜拉桥的索力优化方法；提出综合考虑体内、体外预应力钢筋以及拉索的优化思路,有利于改善PC主梁空间应力状态及发挥整体结构的经济性；结合部分斜拉桥主梁的大刚度特点,探讨了稀索体系和在部分斜拉桥中应用的可能性。更多还原

【Abstract】 Partially cable-stayed bridge, as an exemplification for combined bridges, become more striking and be recognized gradually by civil engineering for its design concept of "use cables to help the main girder". This bridge type is usually suitable for middle-span bridges and full of flexibility.Following the success of Fujian Zhangzhou Combat Readiness Bridge and Wuhu Changjiang Bridge, there have been dozens of such bridges in operation at home. Among them, the PC box girder with big width has gradually became the mainstream although its spatial mechanical properties have not been fully understood. Focusing on Chongqing Jiayue Bridge, which is a partially cable-stayed girder bridge with double outward-inclined cable planes, this dissertation deeply discussed many problems as following mainlined by preliminary design theories and special mechanical behaviors of the PC box girder with long-cantilever slab.1. Studies on the conceptual design and approximate calculation formulas.Based on the exiting research achievements on defining methods of partially cable-stayed girder bridge, and taking intrinsic character of "cable-stayed girder" bridge into account, this paper systematically expounds the determining principle of total design parameters and the key point of mechanical design of main beam. Furthermore, approximate formulas about internal forces of girder and cables under dead load and traffic load are deduced on the assumption of beam on elastic foundation.2. Studies on parametric behaviors of Partially Cable-stayed Girder Bridges based on trial designs in several kindsOn the basis of research results in the conceptual design stage, this paper carries on the analysis of the importance of parameters which affect the structural behavior of the partially cable-stayed girder bridge, and the coMParative analysis of several important structural parameters which affect the integral structural behavior of the partially cable-stayed girder bridge including the main stiffness, the length of no-cable girder, the initial cable tension, etc. According to the suggestion of this paper, the parameter optimization of partially cable-stayed girder bridge should take the requirement of different stages into account separately. Then this paper proposes a new optimal design method of variable stiffness (height) girder, and carries on a large amount of computational analysis about the iMPact on internal structural behavior caused by variable length of no-cable girder and variable initial cable tension. The research results play an important referential role to make sure the design key points of main girder and bring the superiority of partially cable-stayed girder bridge into further play.3. Study on the key problems of the PC box girder based on three dimensional analysisBackground of Chongqing Jiayue Bridge with double outward-inclined cable planes, this paper carries on the spatial structure simulation computes in all construction stages. Furthermore, to discusses the longitudinal and transverse deformation and stress distribution of flange-slab under the combined loads, especially the cable force with9800kN each. This paper also propose the reinforcement configuration method based on the stress of all construction stages which is the essential method to ensure the structural secure.4. Study on shear lag effect on the PC box-girder with big-width and long-cantilever slabThis paper coMPares the applicability of different researching methods on shear-lag effect for the PC box-girder with long-cantilever. Taking combined loads effect into account, including dead-weight, prestress, cable tension, the hanging basket, concrete shrinkage and creep, etc. this paper analyzes share lag effect on the roof in simulation cantilever construction processes of the girder, and indicates that share lag effect on area of the girder close to the tower in construction stage should not be ignored, although such effect would become weak in use stage.5. Study on single segment model test for the anchor structure of PC girderIn order to verify the concrete anchor region’s safety under9800kN cable force(that is each cable’s initial tension), a single girder segment trial model on1:3scales was carried out, First, according to the calculation results all of control points were decided; Then, to test the stress and deformation of such control points in scheduled gradating conditions; Furthermore, to coMPare the measured and the calculated values; Final, this paper suggests a reasonable improvement measure for the anchor region of the girder.6.Study on the cable tension optimal design of partially cable-stayed PC girder taking prestress effect into accountIn the paper, many optimization methods of cable force are systemically studied and summarized. Associated with the ideal final and construction stages used to be achieved by stressing all stay cables just one time, it is suggested that the forward cable-tension optimal method based on boosting prestress reinforcement efficiency of PC girder. Another suggestion was synthetically applying internal prestressing, external prestressing and cable force. Besides these, because of the girder’s stiffness, applying dilute cable system into the partially cable-stayed girder bridge. would be impossible.更多还原