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为了研究超高层建筑横风向气动刚度,进行了多自由度气弹模型试验,以直接测量模型在不同风速下的振动频率,用该频率相对于自振频率的改变量作为气动刚度的评估指标。分析了结构阻尼比、风场粗糙度、模型密度、折算风速、高宽比、涡振位移等因素对气动刚度的影响。结果表明:在共振临界风速附近,气动刚度造成风振频率改变量可达自振频率的10%;频率改变量随折算风速呈“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,折算风速大于12时,频率改变量保持稳定且略小于结构自振频率。由于涡振位移和气动刚度的相互作用,结构阻尼比越小、风场紊流度越小、模型高宽比越大、密度越小则频率改变量随风速变化的“V”字形越尖锐。最后提出了名义折算风速和实际折算风速的概念,并建立了气动刚度的简化估算模型。
In order to study the aerodynamic stiffness in the crosswind direction of a high-rise building, a multi-degree-freedom aeroelastic model test was conducted to directly measure the vibration frequency of the model at different wind speeds. The change of the frequency relative to the natural frequency was taken as the evaluation index of the aerodynamic stiffness. The effects of structural damping ratio, wind field roughness, model density, converted wind speed, aspect ratio, vortex-induced displacement on aerodynamic stiffness were analyzed. The results show that the change of wind vibration frequency is up to 10% of the natural frequency in the vicinity of the critical wind speed of resonance, and the change of frequency changes with the converted wind speed. When the wind speed is less than 8, the frequency changes The amount of change is usually positive, and the maximum frequency change is near the critical wind speed. When the wind speed is more than 12, the frequency change remains stable and slightly less than the natural frequency of the structure. Due to the interaction between vortex-induced displacement and pneumatic stiffness, the smaller the structural damping ratio is, the smaller the wind turbulence is, the larger the aspect ratio is and the smaller the density is, the more the frequency changes with the wind speed sharp. Finally, the concepts of nominal wind speed and actual wind speed are put forward, and a simplified estimation model of pneumatic stiffness is established.