悬索桥施工期主缆—猫道系统驰振及静风稳定性的干扰效应

发布时间：2018-08-17 14:13

【摘要】：在强风作用下,部分大跨悬索桥施工期主缆在绳索的张拉下振动幅度较大,严重影响施工工期;且因施工期主缆并非成桥时圆形截面形式,存在驰振失稳的可能性;同时,猫道的存在对施工期大尺度尖顶型主缆静风系数存在气动干扰效应问题,可能影响主缆的驰振性能。因此,进行大跨径悬索桥暂态结构抗风性能具有较高的理论和实际意义。鉴于此本文进行了如下主要研究工作:1.本文采用CFD数值模拟方法,参考某大桥施工期猫道和主缆设计参数,首先结合猫道风洞试验的结果,验证了数值模拟参数设置的正确性;然后分别研究了不考虑猫道和考虑猫道影响时,施工期三角形、五边形和尖顶型形状主缆的阻力和升力系数;最后利用登哈托准则,计算了施工期主缆不同工况的驰振力系数。结果表明:随着主缆索股层数的不断增加,施工初期呈倒三角形形状的主缆阻力系数不断减小,升力系数逐步增加;施工中期呈五边形形状的主缆阻力系数不断增加,升力系数逐步减小;施工后期呈上尖顶型形状的主缆阻力系数不断增加,升力系数总体上有减小趋势;通过与无猫道工况的对比可知,考虑猫道时会造成施工期主缆阻力和升力系数相应地减小,且计算主缆驰振力系数时,不能忽略猫道的气动干扰效应。2.研究表明,悬索桥施工期暂态主缆存在驰振失稳的可能性,且因施工期主缆处于主缆施工脚手架猫道的半包围之中,猫道设计参数的变化势必对施工期主缆的驰振性能产生重要影响。为研究猫道设计参数对施工期主缆驰振性能的影响,本文以某大跨径悬索桥施工期不同工况大尺度尖顶型主缆为研究对象,以猫道风洞试验结果为参照,以流体力学软件Fluent为工具,首先验证了数值模拟参数设置的正确性;进而研究了猫道高度、猫道宽度、猫道侧网透风率、猫道底网透风率,以及猫道面层与主缆底部间距等参数影响下施工期主缆的气动力系数;最后运用登哈托准则分析了猫道设计参数对施工期主缆驰振性能的影响。研究结果表明:(1)猫道宽度、猫道护栏高度以及猫道面层与主缆底部间距对施工期主缆阻力系数影响不大,但会导致升力系数变大;当主缆与猫道面层间距为84cm、猫道宽度为4.5m、猫道护栏高度为1.3m时,对驰振失稳预防较为有利;(2)猫道侧网透风率可导致施工期主缆阻力系数变小,但升力系数较无规律;当猫道侧网透风率为50%时,对驰振失稳预防较为有利;(3)猫道底网透风率对施工期主缆阻力和升力系数影响较为敏感;当猫道底网透风率为70%时对驰振失稳预防较为有利;(4)当猫道面层与主缆底部间距为0.84m、猫道高度为1.3m、猫道宽度为4.5m、猫道侧网透风率为50%和猫道底网透风率为70%时,主缆发生驰振失稳可能性最小。3.由于大跨径悬索桥施工期尖顶型主缆与猫道间存在气动干扰效应,且主缆索股层数在施工期不断增加,因此,猫道的气动性能和静风稳定性也随之变化。本文以某大跨径悬索桥施工期尖顶型主缆和猫道为背景,研究了施工期尖顶型主缆对猫道静风稳定性影响问题。首先,参照该桥猫道风洞试验的结果,验证了数值模拟参数设置的正确性;进而计算了施工期尖顶型主缆不同阶段猫道的三分力系数;最后对ANSYS软件进行了二次开发,考虑了猫道的几何非线性和风荷载非线性,进行了施工期尖顶型主缆不同阶段猫道静风稳定性分析。研究结果表明:考虑施工期尖顶型主缆影响时,(1)猫道阻力系数和扭矩系数呈先增大后减小的趋势;(2)猫道升力系数在负攻角范围内呈先减小后增大趋势,但在正攻角范围内变化不大;(3)随尖顶型主缆的施工进程,猫道失稳临界风速呈先减小后增大,成桥阶段又减小的趋势。其中,15#工况失稳临界风速接近大桥施工阶段和成桥状态10米高度处的空气静力稳定性检验风速,施工时应注意加强观测,必要时须采取抗风保护措施。
[Abstract]:Under the action of strong wind, the vibration amplitude of the main cable of some long-span suspension bridges under the tension of the cable is large, which seriously affects the construction period; and because the main cable is not a circular section when the bridge is completed during the construction period, there is the possibility of galloping instability; at the same time, the existence of catwalk has the aerodynamic interference effect on the static wind coefficient of the large-scale pointed main cable during the construction period. Therefore, it is of great theoretical and practical significance to study the wind resistance of the transient structure of long-span suspension bridges. In view of this, the following main research work has been carried out in this paper: 1. In this paper, CFD numerical simulation method is used to refer to the design parameters of catwalk and main cable during the construction period of a bridge. The test results verify the correctness of the numerical simulation parameters. Then the drag and lift coefficients of triangle, Pentagon and cusp-shaped main cables during construction without considering catwalk and catwalk are studied. Finally, the galloping force coefficients of main cables under different working conditions during construction are calculated by using Denharto criterion. As the number of strands of the main cable increases, the resistance coefficient of the main cable in the inverted triangle shape decreases and the lift coefficient increases gradually in the initial stage of the construction; the resistance coefficient of the main cable in the pentagon shape increases and the lift coefficient decreases gradually in the middle stage of the construction; the resistance coefficient of the main cable in the upper cusp shape increases and the lift coefficient increases continuously in the later stage of the construction. Comparing with the working condition without catwalk, the drag and lift coefficients of the main cable will decrease correspondingly when the catwalk is considered, and the aerodynamic interference effect of the catwalk can not be neglected when the galloping force coefficients of the main cable are calculated. In order to study the influence of catwalk design parameters on the galloping performance of main cables during construction period, a large-scale pointed main cable of a long-span suspension bridge under different construction conditions is selected as the main cable in this paper. Based on the wind tunnel test results of catwalk and the fluid dynamics software Fluent, the validity of numerical simulation parameters was verified firstly, and then the influence of catwalk height, width, side net ventilation rate, bottom net ventilation rate and the distance between surface layer and bottom of main cable on the main cable under construction was studied. The results show that: (1) the width of the catwalk, the height of the catwalk guardrail and the distance between the catwalk surface layer and the bottom of the main cable have little effect on the drag coefficient of the main cable during the construction period, but the lift coefficient will become larger when the main cable and the catwalk surface are used. When the distance between layers is 84cm, the width of catwalk is 4.5m, and the height of catwalk guardrail is 1.3m, it is more advantageous to prevent galloping instability; (2) the ventilation rate of catwalk side net can reduce the resistance coefficient of main cable during construction period, but the lift coefficient is irregular; when the ventilation rate of catwalk side net is 50%, it is more advantageous to prevent galloping instability; (3) the ventilation rate of catwalk bottom net is beneficial to the construction period. The main cable resistance and lift coefficient are more sensitive; when the ventilation rate of catwalk bottom net is 70%, it is more advantageous to prevent galloping instability; (4) when the distance between catwalk surface layer and main cable bottom is 0.84m, the height of catwalk is 1.3m, the width of catwalk is 4.5m, the ventilation rate of catwalk side net is 50% and the ventilation rate of catwalk bottom net is 70%, the main cable is most likely to gallop instability. 3. The aerodynamic performance and static wind stability of the catwalk vary with the increase of the number of layers of the main cables during the construction period because of the aerodynamic interference effect between the pointed main cables and the catwalk during the construction period of the long-span suspension bridge. The influence of main cable on the static wind stability of catwalk is studied. Firstly, the correctness of numerical simulation parameters is verified by referring to the wind tunnel test results of the catwalk of the bridge; then the three-component coefficients of the catwalk at different stages of the construction period are calculated; finally, the ANSYS software is redeveloped, considering the geometric nonlinearity and wind load of the catwalk. The results show that: (1) the resistance coefficient and torque coefficient of catwalk increase first and then decrease; (2) the lift coefficient of catwalk decreases first and then increases in the range of negative angle of attack, but in the case of positive angle of attack. (3) With the construction process of the top-type main cable, the instability critical wind speed of catwalk first decreases and then increases, and then decreases at the bridge completion stage. Wind protection measures must be taken.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U448.25

【相似文献】