方形截面超高层建筑的横风向气动阻尼风洞试验研究

Experimental study on across-wind aerodynamic damping of square super-high-rise building

通过10个方形截面超高层建筑气动弹性模型的风洞试验,利用随机减量法从模型的风致加速度响应中识别了横风向气动阻尼比,通过与前人相关研究成果的比较,验证了识别结果的正确性。在此基础上,研究了方形截面超高层建筑横风向气动阻尼的变化规律,考察了结构阻尼比、质量密度比、广义刚度对建筑结构气动阻尼比的影响。研究结果表明:来流的折减风速、风致响应的振动幅值和质量密度比是影响建筑横风向气动阻尼比至关重要的参数;在低于涡激共振风速的低折减风速区,横风向气动阻尼比与振动幅值和质量密度比成反比,而广义刚度和结构阻尼比通过影响结构振幅和折减风速的方式间接对气动阻尼比造成影响;在高折减风速区,横风向气动阻尼比常常表现为负值,主要与风致响应的气动稳定性有关。基于这些研究数据,对B类风场下高宽比为8的方形截面超高层建筑,拟合了适用于低折减风速区的横风向气动阻尼比经验公式,供工程设计人员参考。

Across-wind aerodynamic damping ratios are estimated from wind-induced acceleration responses of 10 aeroelastic models of square super-high-rise building by the random decrement technique. Their validity is proved by comparing with previous research achievements. Characteristics of across-wind aerodynamic damping ratios of square high-rise building are studied. Effects of structural damping ratio, mass ratio and generalized stiffness on across-wind aerodynamic damping ratios are investigated. Results indicate that reduced wind velocity of incident flow, wind-induced vibration amplitude of building and mass ratio are the most impollant parameters for across-wind aerodynamic damping ratio. At reduced wind velocity lower than vortex shedding velocity, aerodynamic damping ratio is inversely proportional to vibration amplitude and mass ratio, while generalized stiffness and structural damping ratio indirectly affect aerodynamic damping ratio by executing influence on vibration amplitude and reduced wind velocity. At high reduced wind velocity, aerodynamic damping ratio is negative in most cases and it is closely related to aerodynamic stability. According to the database, empirical aerodynamic damping function is proposed to estimate across-wind aerodynamic damping ratio at low reduced wind velocity for square super-high-rise buildings.