矩形截面超高层建筑横风向气动阻尼的风洞试验研究

摘要

The mechanism of aerodynamic damping in cross-wind is very complicated.No widely adopted theory and sophisticated method are available up to date,with no relevant guidelines in the load standards and codes in most countries.In order to investigate the effects of roughness exposure,aspect ratio and side ratio on across-wind aerodynamic damping ratio,the random decrement technique is used to evaluate across-wind aerodynamic damping ratios from wind-induced acceleration responses of 15 aeroelastic models.The evaluated results are compared with previous research achievements.The characteristics of across-wind aero-dynamic damping ratio of rectangular high-rise buildings are studied.Results indicate turbulence intensity and side ratio are the most important factors affecting across-wind aerodynamic damping ratio.Aspect ratio indirectly affects aerodynamic damping ratio through making change of response amplitude.For the variation rule of aerodynamic damping ratio with reduced wind velocity,both of the magnitudes of positive and nega-tive peaks decrease as turbulence intensity increases.Meanwhile,reduced wind velocity,from which aerody-namic positive damping ratio changes to negative damping,increases as turbulence intensity increases.Side ratio has significant influence on across-wind aerodynamic damping ratio,and completely different tendency are observed for B/D <1,B/D =1 and B/D >1.According to the database,empirical aerodynamic damping functions are proposed to estimate aerodynamic damping ratios at low reduced velocities for rectangular su-per-high-rise buildings with an aspect ratio in the range of 5 to 10,a side ratio of 1/3 to 3,and lateral turbu-lence intensity varying from 0.67% to 17.06%.%通过15个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，并通过比较验证了识别结果的正确性。在此基础上，研究了矩形截面超高层建筑横风向气动阻尼的变化规律，考察了湍流度、高宽比、宽厚比对建筑结构气动阻尼比的影响。研究结果表明：来流湍流度和建筑的宽厚比是影响高层建筑横风向气动阻尼比至关重要的参数，而高宽比主要通过改变振动幅值来影响横风向气动阻尼；横风向气动阻尼比随折减风速变化的正负峰值大小基本随来流湍流度的增大而减小，气动阻尼比由正转负对应的折减风速随湍流度的增大而增大；宽厚比对横风向气动阻尼比的影响很大，当 B/D＜1、B/D＝1及 B/D＞1时，气动阻尼比的变化规律几乎完全不同。基于这些研究数据，对横风向湍流度为0．67％～17．06％的风场中、高宽比5～10及宽厚比1/3～3之间的矩形截面超高层建筑，给出了适用于低折减风速区的横风向气动阻尼比经验公式。