【作者】 刘慕广；

【导师】 陈政清；

【作者基本信息】 湖南大学 ， 桥梁与隧道工程， 2009， 博士

【摘要】 本文主要研究了桥梁结构中常见的两类大长细比构件的风振特性。一类为大跨拱桥、桁架桥中常见的H型和矩形截面杆件,文中以直立的拱桥吊杆为对象,研究了这两种截面构件在大攻角下的风振特性;另一类为悬索桥、斜拉桥中常见的圆截面索缆结构,文中以无吊杆的两串列主缆为对象,研究了上下游主缆间的气动干扰机理。本文主要进行了以下研究:1、依据风洞试验和理论分析提出了直立H型杆件的大攻角扭转颤振理论,证明了某大跨度拱桥发生的吊杆风振为扭转颤振,而不是涡激共振。腹板开孔不能提高H型杆件的颤振临界风速,但适度开孔可改善驰振和涡激共振特性。通过16组正交试验研究了高宽比、腹板及翼板开孔率三种截面参数变化下H型截面吊杆的风振特性,应用方差分析理论综合评价了三参数对H型杆件颤振、驰振及涡振特性的影响。合理的改变截面形式,可有效提高颤振、驰振、涡振的起振风速,减小涡振锁定区间和涡振幅值。2、风洞试验研究表明矩形吊杆具有较大的抗扭转颤振的能力,但存在驰振临界风速较低、涡振振幅较大及涡振锁定区间较宽的问题。为此,提出了矩形杆件内表面敷设阻尼层减振的措施。通过模型试验验证了该减振措施的可行性,并对矩形吊杆敷设阻尼层后的结构阻尼特性进行了数值模拟。3、应用三自由度强迫振动装置,解决了大攻角下弹性悬挂自由振动时存在的竖向运动失真问题,准确识别了大攻角下的H型和矩形断面杆件气动导数。对比研究表明竖向运动失真导致的气动导数识别误差随攻角增大而增大,从而肯定了强迫振动法用于大攻角气动导数识别的优越性。应用强迫振动装置上的天平测量节段模型的气动力时程曲线,实现了随攻角连续变化三分力系数的测量,并由升力时程曲线推算了多组H型和矩形断面的Strouhal数。这些工作进一步扩大了强迫振动法的应用范围。4、推导了常见H型和矩形细长杆件的抗风设计公式,以限制杆件的适用长度为原则,提出了抗风设计的建议。5、结合气弹模型试验和CFD数值模拟技术研究了串列主缆间的气动干扰。试验表明下游缆会发生面外振动强于面内振动的尾流驰振,且间距、风偏角、风攻角及固有频率对尾流驰振的起振风速影响显著。CFD模拟表明雷诺数并不影响下游缆横风向力的变化趋势,实桥与模型对应雷诺数下尾流驰振起振风速的数值计算结果均稍高于模型试验的结果。更多还原

【Abstract】 The wind-induced vibration characteristics of two classes of structural elements with large slenderness ratio that are frequently used in the bridge are studied in this paper. The first of them is H-shaped and rectangular section members that are often applied in the long span arch bridge and truss bridge. The suspenders of arch bridge with these two sections subject to large wind attack angle are chosen to study the wind-induced vibration characteristics. The other kind is cable with circular section that is commonly used in the suspension bridge and cable stayed bridge. The aerodynamic interference mechanism between the upstream and downstream main cables without suspenders is investigated. Some main contributions in this paper are as follows:1. The torsional flutter theory of vertical H-shaped member for the large wind attack angle is developed based on the theoretical research and wind tunnel tests. It is proved that the observed wind-induced vibration of suspenders in one long span arch bridge is torsional flutter rather than vortex-excited resonance. The slots of web can’t increase the flutter critical wind speed, but it is helpful to improve the characteristics of galloping and vortex-induced vibration by modest slot ratio. The wind-induced vibration characteristics of suspender with different height-width ratios, web and flange plate slot ratios are evaluated by 16 groups of orthogonal tests. The variance analysis theory is used to illustrate the effects of the three parameters in the flutter, galloping and vortex-induced vibration of suspender. Reasonable change of section can effectively enhance the onset wind velocity of flutter, galloping and vortex-induced vibration, and decrease the lock-in wind speed range of vortex-induced vibration as well as the amplitude of vortex-induced vibration.2. Wind tunnel tests has shown that suspenders with rectangular section have excellent stability of torsional flutter; but facing some other problems such as lower critical wind speed of galloping, rather larger amplitude and lock-in wind speed range of vortex-induced vibration. Therefore, covering the inner-surface of suspender with extra damping layer is presented to control wind-induced vibration. The model test is used to verify the feasibility of this control strategy. Furthermore, the damping characteristics of suspender with damping layer are evaluated by numerical simulation. 3. The forced vibration equipment with three degrees of freedom is applied to solve the distortion problem of vertical motion in free elastic suspension method, and the flutter derivatives of H-shaped and rectangular sections under large attack angle are accurately identified from the forced vibration testing data. The comparative study shows that the distortion of vertical motion will lead to the identification error of flutter derivatives, and the error increases with the angle of attack. Therefore, the forced vibration method of identifying flutter derivatives with large attack angle is confirmed to have excellent performance. The aerodynamic forces of section model are measured by the force balance of forced vibration equipment, which is further used to estimate the Strouhal number of H-shaped and rectangular sections, and the measurements of steady aerodynamic force coefficient continuously varying with attack angles are realized. All these work have extended the application field of force vibration method.4. The wind resistant design formulas of commonly used H-shaped and rectangular structural elements with large slenderness ratio are derived to define the upper limit of the practical length of these elements. Meanwhile, some suggestions of wind resistant design are given.5. The aerodynamic interference between two parallel main cables is studied by combining aeroelastic model tests with computational fluid dynamics (CFD) technology. Wind tunnel tests have shown that wake galloping with stronger out-plane than in-plane vibration can be seen in the downstream main cable, and the distance between the upstream and downstream main cables, wind yaw angle, wind attack angle as well as natural frequency of cable have a great influence on the critical wind velocity of wake galloping. CFD simulations have indicated that Reynolds number doesn’t have effect on the trend of changes in across-wind force, and moreover, the critical wind speed of wake galloping of prototype and model with corresponding Reynolds number is a little bit higher than that in the model tests.更多还原