超高层建筑多自由度气弹模型的优势及制作方法

Advantages and making method of a super high-rise building's multi-DOF aero-elastic model

首先简要对比了测力天平、刚性模型测压、强迫振动、气动弹性模型等四种试验手段的特点,然后着重分析了底部弹性支撑的摆式气弹模型和多自由度气弹模型试验结果的差异,分析发现,对超高超柔的方截面建筑而言,摆式模型所得的横风向风致响应在小风速下比多自由度模型略大,而在包含横风向共振风速在内的大风速下则明显大于多自由度模型,其气动阻尼特性、气动刚度特性和表面风压相干性等倾向于使摆式模型出现相对较大的风致响应。究其原因,是因为只模拟一阶模态的摆式模型在反映流固互制气弹效应方面不够真实且不及多自由度模型精细,即参振模态的不同(包括参振模态数量、高阶与低阶平动频率比、扭转与平动频率比)会使振动形式发生改变,进而影响振动时的气弹效应并改变振动位移。在此结论的基础上,提出了多自由度气弹模型改进设计方法,该方法考虑了低阶与高阶频率比、平动与扭转频率比的可调性,同时解决了模型弯剪振型成分的可控制性和阻尼调节等问题,以期为实际项目的多自由度模型制作和相关研究提供便利和参考。

The characteristics of four test methods including high frequency force balance, forced vibration, aero- elastic model and rigidity model manometric test were compared firstly, then the differences between the test results of elastic body-based pivoted aero-elastic model （SDOF model） and muhi-DOF aero-elastic model （MDOF model） tests were analyzed penetratingly. Wind tunnel tests revealed that the across-wind displacement of SDOF model is usually larger than that of MDOF model, especially, when the wind speed is close to the critical velocity of the crosswind resonance, and the reason for this phenomenon is the difference between vibration modes of two models, it sensitively changes the aero-elastic effects including aerodynamic damping, aerodynamic stiffness and wind pressure correlation. Finally, an improved design method of MDOF model supported with one centered column and four ambient columns was proposed base on above conclusions, it gave enough attention to the adjustability of high order frequency, torsional frequency and structural damping.