超高层建筑涡振过程中体系振动频率

Investigation on VIV system vibration frequency of super high-rise building

为了研究超高层涡激振动过程中的频率飘移问题,进行多自由度气弹模型和部分底部弹性支撑的摆式模型试验,以直接测量发生涡激共振前后振动体系的频率变化情况,分析影响频率改变量的几个因素,探讨频率改变量与涡致位移之间的互制现象.分析表明,当高层建筑较为高柔时,涡振过程中频率漂移现象不可忽略,振动体系频率随折算风速呈"V"字形变化,在折算风速小于8时,频率改变量通常为正,在共振临界风速附近频率改变量最大,之后又回升到比自振频率略小的相对稳定的值.在同一流场中,斯克拉顿数越大的模型正频率改变量越大,而负频率改变量则相反;不同流场中,流场越粗糙振动频率和位移曲线的尖峰现象越不明显,且正频率改变量越小,而大折算风速时负频率改变量越大.

In order to study the system vibration frequency of super high-rise building in the process of vor- tex induced vibration（VIV）, which may be deviated from natural frequency by aerodynamic stiffness and aerodynamic mass, MDOF aeroelastic model tests and SDOF aeroelastic model tests were carried out to measure the frequency of vibration system directly before and after VIV. The influences of wind field category, Scruton number, reduced wind speed, as well as VIV displacements to system frequency were analyzed. It was found that the magnitude of frequency drift phenomenon can not be ignored when a building is very tall and flexible, and with the increasing of reduced wind speed, the drift magnitude varies like V shape. When the reduced wind speed is less than 8, the drift magnitude of the frequency is normally positive. When the reduced wind speed is close to the critical reduced wind speed of resonance , the drift magnitude of the frequency turns to negative and reaches minimum at the critical reduced wind speed of resonance, and then persists in a stable value which is slightly smaller than the natural frequency along with the increase of reduced wind speed. In smooth and turbulent flow fields, the positive drift magnitudes of the frequency are increasing and negative drift magnitude of the frequency are decreasing as Scruton number increases. So it is necessary to establish a new vortex-induced response assessment model for high-rise flexible building with consideration of frequency drift by aerodynamic stiffness and aerodynamic mass.