【作者】 贾宁；

【导师】 刘健新；

【作者基本信息】 长安大学 ， 桥梁与隧道工程， 2008， 博士

【摘要】 悬索桥施工猫道是施工人员机械进行主缆施工作业的高空脚手架,是大跨度的柔性透风索结构,结构刚度小,对动力作用敏感。猫道在风荷载和施工人员行走时若产生较大变位,将导致牵引索股的扭转、鼓丝、散丝现象,会影响成桥后主缆的受力甚至主缆的施工安全。随着我国跨海连岛工程的建设,恶劣施工环境中的特大跨度悬索桥及其主缆施工猫道将不断出现,因此系统深入研究猫道的抗风减振性能,发展行之有效的猫道抗风减振技术,有十分重要的意义。本文系统全面探讨猫道对风反应特点,国内外首次进行猫道结构的涡振性能风洞试验,可知避免猫道产生涡激振动的侧网临界透风率为70%,底网透风率大小对涡振性能没有影响,所采用的试验方法和试验结论对于研究类似透风结构的涡振性能有一定参考价值,分析猫道升力系数和阻力系数的特点,可知其不可能发生驰振现象。采用节段模型静力三分力风洞试验结果和有限元分析相结合的方法进行猫道非线性静风响应分析,根据猫道承重绳的张力和位移随风速的变化规律,可知猫道发生静力扭转发散的内在原因是由其所受的静力三分力的特点决定的,国内外首次对猫道减振构造(包括抗风缆系统、水平制振索、抗风门架和斜索、斜拉索和外索)的抗风性能进行系统的参数化分析,得出抗风减振构造设计参数变化时对猫道在风荷载作用下位移响应及静力扭转发散临界风速的影响,为工程技术人员设置猫道减振构造提供理论参考和依据。在国内外首次进行猫道的人行侧向振动分析,通过类比风致振动中的涡激振动,提出人行侧向振动的自激力特性,借鉴人行桥侧向振动的研究结论,通过一定修正应用到猫道中,可计算避免发生猫道-行人同步侧向振动的临界行人数量和密度以及猫道所需的阻尼,也可估算一定行人密度时猫道的侧向位移响应。联结绳是一种增大猫道阻尼的简便有效的方法,其制振效果的影响因素包括联结绳自身的振动频率、阻尼、质量、联结位置,在国内外首次进行联结绳的参数化试验研究,根据试验结果,综合考虑各种因素,为保证联结绳制振效果,建议联结绳与猫道面层之间的斜交角在40°～50°范围内,联结绳的质量在猫道面层质量的1%左右取值,联结绳频率尽可能与猫道面层固有频率接近,联结绳的阻尼越大,制振效果越好。更多还原

【Abstract】 Catwalk of suspension bridge is the scaffold at high altitude erected as the sidewalk for constructor and machines. With long span and low stiffness catwalk is sensitive to dynamic forces. Large displacements induced by wind and walking constructors can lead to torsion, drumming and dispersing of cable wires, which has bad effects on the performances of cables. The torsional collapse of catwalk can result in the danger of constructor and machines. Along with the construction of suspension bridges spanning over sea and connecting islands, more and more long-span catwalks under bad construction conditions have appeared. So it is obviously significant to study wind-resistant and vibration-control performance and develop effective relative techniques for catwalks.Characteristics of reaction to wind for catwalk are comprehensively studied in this dissertation. The wind tunnel tests are conducted to study the vortex produced by the side cover and bottom cover of catwalks. It is verified that the vortex-induced vibration of catwalks can be avoided if the wind penetration rate of side cover is more than 70%. The wind penetration rate of bottom cover has no influence on this conclusion. The test method and conclusion can help to study the similar structure that allows wind penetrating. The gallop vibration cannot happen to catwalks according to the characteristics of lift force and resistant force tested through wind tunnel tests.Nonlinear analysis is performed by FEM method using sectional model tests results. According to the inner force and displacement of catwalk rope exposed to the wind load, it is indicated that near the critical wind velocity for torsional collapse the stress of the catwalk rope begins to lack because of upward air lifting, and then the resisting force of catwalk is less than the air moment. This is the cause of torsional collapse for catwalk. Nonlinear analyses are conducted for catwalk with the vibration control conformations including storm ropes, horizontal ropes, stay ropes and outside ropes. The displacements and critical wind velocity for torsional collapse are also calculated to compare the vibration control effects. Based on these conclusions the conformations above can be installed on catwalks by designers.The human-induced lateral vibrations on catwalks are analyzed in this dissertation. By comparing to vortex-induced vibration for bridges it is indicated that human-induced lateral vibration has a self-excited nature. With reference to the research of human-induced lateral vibration on footbridges the methods are amended to be suitable for analyzing this vibration on catwalks. The analysis leads to an equation for predicting critical number of pedestrians and needed damp for catwalk to avoid synchronized excitation. The lateral displacement of catwalks with a certain number of pedestrians can also be estimated through the analysis.Connecting rope is a simple and effect method for increasing the damp of catwalks. The vibration control effects of connectiong ropes are influenced by natural vibration frequency, damp, mass and connecting position. Vibration tests are conducted to study the relationship between damp increasing level and the factors above. Considering vibration control effects and construction practice, the angle between connecting rope and catwalk longitudinal axis should be between 40°and 50°. The mass of connecting rope should be one percent of the catwalk mass. The natural vibration frequency of connecting rope and catwalk should be similar to the largest extent. The vibration control effects get better with the damp of connecting rope increasing.更多还原