长宽比2∶1矩形截面高层建筑全风向气动阻尼试验研究

Experimental study on aerodynamic damping of tall buildings with 2∶1 rectangular cross section under full-direction wind action

由于高层建筑阻尼小、频率低,易在风荷载作用下发生明显的气动弹性效应,出现不可忽略的气动负阻尼比。为此,考虑高层建筑的一阶线性弯曲模态,制作了长宽比2∶1的矩形截面高层建筑的单自由度气动弹性模型,模型比例1/600。进行了全风向下气弹模型风洞试验,每个风向测量了10个试验风速下的建筑顶部加速度响应,并采用随机减量方法,对矩形截面高层建筑气动阻尼比进行识别。研究结果表明:对于长宽比2∶1的矩形截面高层建筑,强轴方向的风致加速度响应远大于弱轴方向;两个主轴方向的顺风向气动阻尼比均为正值,但强轴方向的横风向气动阻尼比为负值,无量纲临界风速约为5.5;仅采用横风向气动阻尼比结果,可以很好地反映全风向的气动阻尼特性。

Tall buildings experience aeroelastic effects under the wind action due to its low natural frequency and structural damping,and significant aerodynamic damping ratio arises. Considering the first order linear sway mode,a single degree-of-freedom aeroelastic model of tall buildings with 2∶ 1 rectangular cross section was manufactured with a geometrical scale of 1 /600,and a series of wind tunnel tests were carried out to measure the acceleration at the building top under ten different wind speeds of each wind attack angle. Random decrement technique（ RDT） was adopted to identify the aerodynamic damping ratio of the building model. The aerodynamic damping ratio in along-wind and across-wind directions obtained agrees well with that from literatures. The results show that the acceleration responses in the strong-axis are obviously larger than those in the weak-axis for tall buildings with 2∶ 1 rectangular cross section. The along-wind aerodynamic damping ratios in strong and weak axes are both positive. However,obvious negative aerodynamic damping ratio is observed in the direction of structural strong-axis over the non-dimensional critical wind velocity of 5. 5. The feature of aerodynamic damping ratio in across-wind direction can represent that in full-direction wind.