安装椭圆形灯具和矩形线盒的斜拉索驰振

Galloping of Stay Cables Installed with Elliptical Lamp and Rectangular Box

针对亮化灯具引起的斜拉索振动问题,以某安装椭圆形灯具和矩形线盒的斜拉索为工程背景,研究了驰振特性及增加结构阻尼对驰振的抑制效果.首先,进行了节段模型测力风洞试验,测量了安装灯具斜拉索的三分力系数,通过驰振力系数初步预测了发生驰振的风攻角范围;然后,分别进行了二维和三维节段模型测振风洞试验,测量了安装灯具斜拉索风振响应随风攻角、风速等的变化规律,探讨了阻尼比对提高驰振临界风速的影响规律.结果表明:安装椭圆形灯具和矩形线盒的斜拉索的平均阻力和升力系数最大分别可达1.8和1.5,静风荷载比未安装灯具时可增大83%;局部凸起的点光源对安装灯具斜拉索的气动力影响很小;二维斜拉索的最不利风攻角为8°,驰振力系数低至-7.9,阻尼比为0.1%时驰振临界风速为21.8 m/s;三维斜拉索的起振风偏角范围为40°~56°、186°~196°,面内和面外都有较大振动;阻尼比为0.1%时起振风速低至4.7 m/s;起振后,随风速的增大,振幅线性增加,折减风速达到77时,无量纲位移可达到2D(D为斜拉索直径);增大阻尼在相同风速下可降低振动的幅度;阻尼比小于0.8%时,增加阻尼对驰振临界风速的提高作用有限;当阻尼比增大到1.0%时,能够有效抑制安装椭圆形灯具和矩形线盒的斜拉索驰振.

Aiming at the problem of stay-cable galloping caused by lighting lamps,the galloping vibration characteristics and the effect of increasing structural damping on galloping-vibration were studied based on the engineering background of a stay-cable installed with an elliptical lamp and a rectangular box.First,the aerodynamic coefficients of stay cable were measured by the force measurement wind tunnel tests.The wind attack angle range of cable vibration was predicted by using galloping force coefficient.Then,2-dimensional and 3-dimensional vibration tests were carried out to measure the critical wind speed of galloping.The influence of damping ratio on vibration was also studied.The test results show that the maximum drag coefficient and lift coefficient of stay cables with elliptical lamp and rectangular box are 1.8 and 1.5,respectively.The static wind load on the stay cable can be increased by 83%.The influence of local bulge point light on the aerodynamic force of stay cable is small.For two-dimensional stay cables,the most dangerous wind attack angle is 8°.The minimum galloping force coefficient is-7.9 and the minimum critical wind velocity is 21.8 m/s.For three-dimensional stay cables,the yaw angle of vibration is 40°~56°and 186°~196°.Both in-plane and out-of-plane vibrations occur.Whenζis 0.1%,the critical velocity is 4.7 m/s.The vibration amplitude increases linearly with the increase of wind velocity.When the reduced wind velocity is 77,the dimensionless displacement can reach 2D(D is the diameter of stay cable).Increasing the damping can reduce the amplitude of vibration at the same wind velocity.When the damping ratio is less than 0.8%,the effect of increasing damping on the critical wind velocity is limited.If the damping ratio is increased to 1.0%,the galloping vibration of stay cables installed with elliptical lamps and rectangular wire boxes can be effectively suppressed.