大高宽比超高层建筑风荷载和风效应控制研究

Super-tall buildings with hundreds of meters height usually have large aspect ratio. Wind effect and vibration control garner particular attention in the wind-resistant design of such structures in strong wind area. Wind-induced vibration control method embraces aerodynamic shape optimization and installing damper. The former essentially considers the effect of change of architectural shape on aerodynamic forces. It is research hotspot in wind-resistant research of structures. However, because of considering too many paremeters, the analyses results are not detailed enough and the value range of a single influence parameters is rather narrow. It cann’t meet the demand of wind-resistant design of super-tall buildings becoming increasingly slender and high. In addition, preliminary research results show that there are significant differences on the characteristics of aerdynamic loads between buildings with large aspect ratio and that with usual aspect ratio. The problems of conventional dampers are covering extra area, high cost and complex implementation. Therefore, in this project , the effects of global and local strategies on aerodynamic forces and wind-induced responses of buildings with large aspect ratio are elaborately investigated. The general rule of effect of changing architectural shape on wind effect is summarized. A new type of damper is adopted in the vibration control of buildings. By elaborate wind tunnel experiment of aeroelastic model with different structural damp ratios, comprehensive evaluation of reducing vibration effects is showed. Those study could further promote the technology of wind-resistant design of super-tall buildings and provide important science support for wind-resistant design of those structures.

数百米量级超高层建筑通常具有大高宽比特性，强风地区风效应及控制措施是此类结构抗风设计中倍受关注的问题。风效应控制主要依靠外形气动优化和阻尼器方法，前者本质上是考虑建筑外形变化对结构气动力的影响，是结构抗风研究的热点，但存在内容过于泛而导致分析结果不够精细、影响参数取值范围偏窄化而使所得结果不能满足日益细高化超高建筑抗风设计的需要，已有的初步研究显示大高宽比超高建筑的气动荷载特性和常规高宽比建筑相比有明显差别；常规阻尼器方法存在实现过程复杂、造价偏高且占用额外空间等问题。因此，提出本项目，通过试验研究大高宽比建筑立面整体和局部变化对结构气动力与风致响应影响，总结建筑外形变化对此类结构风效应影响的一般规律；将一新型阻尼器应用于建筑振动控制，通过不同本底结构阻尼比气弹模型的精细风洞试验对其减振效果进行全面评价。通过研究将进一步促进超高建筑抗风设计的技术进步，为此类结构的抗风设计提供重要科学支撑。

本项目主要对高宽比为9:1且高度在500m以上量级的一系列变截面(线性锥度立面方案和退台收缩方案)超高层建筑进行同步测压风洞试验，考虑角区切角、局部开透风槽、开洞、结构表面粗超度等对结构体型系数、极值风压、气动荷载分布以及风致荷载和响应的影响；提出并合作研制了一套新的两自由度刚性摇摆气动弹性模型试验装置并成功用于某838m高超高层建筑的气动弹性试验。(1)对于立面线性收缩方案，峰值负压有随锥率增加略微减小趋势。切角处理显著增加切角处的峰值负压，锥率越大，切角处的负压也越大，最大增加90%。开启局部透风槽后在其本身位置处形成高负压区，距离增加影响快速消失。从整体上看，建筑侧立面峰值负压分布较为均匀，从而引起建筑底部风压相对较高，这会严重影响常规建筑底部大堂的幕墙设计，应引起关注。(2)线性锥度立面方案使得建筑侧立面由等截面方式的频率相同的整体漩涡变成沿高度频率逐渐增加的连续漩涡，退台方案则变成沿高度若干个频率不同的局部漩涡，切角处理以后原有的较大峰值漩涡脱落基本消失，开启局部透风槽措施有助于削减未切角处理结构的漩涡脱落强度和切角处理结构气动力中和漩涡脱落频率相关的残余能量。(3)立面线性和退台收缩方案最终都可有效地降低超高层建筑的风致荷载，锥率为2.2%、4.4%和6.6%三个不同锥率模型的100年峰值基底弯矩要比等截面正方形模型分别减小44.12%、68.42%、81.85%，四个退台方案的减小效果在75%~79.2%之间。锥率为0.0%、2.2%和4.4%的三个模型经过切角处理以后减小效果分别为65.25%、73.81%和80.93%。在四种不同局部开槽处理策略中，全部开启减小效果最好，接近模态加权气动力(定义为结构归一化高度和气动力之积)中心开启透风槽的效果最优。(4)所研制的气弹模型试验装置具有结构阻尼可定量控制且稳定性好、模型质量模拟方便等创新点。