复杂环境中超大型冷却塔风振机理与等效静风荷载研究

The construction of cooling towers in China tends to be highly largened (the height of towers broke the world record of 200m) and complicated (group of varied towers work parallelly; interference caused by structures around), the problem of wind-induced vibration has become the binding constraint that limits the leap of super-large cooling towers. However,the standards related to the design and construction of cooling towers only provide one single wind-induced coefficient available to those less than 165m and in different topography, meanwhile the reasearch on matching equivalent static wind load was blank. In fact, the wind-induced vibration of super-large cooling towers appears three characteristics: multi-mode combination, multiple distributions of fluctuating wind loads, multiple coupling effects. Furthermore, the resonant and coupling effects of super-large cooling towers under complex condition are apt to be more sharp and significant, therefore, the theory of computation of equivalent stastic wind loads as well as the mathematical model urgently need to be reviewed. For this purpose, aero-elastic model used to simultaneously measure pressure and vibration of super-large cooling towers is supposed to be developed and to obtain the aerodynamic parameter concerning with the effect of self-excited force, and the whole process test simulation of super-large cooling tower from linear vibration to unstable failure under high wind speed. Meanwhile, a refined theoritical approach is expected to be proposed for understanding the general mechanism of wind-induced coupled vibration, and make furthre efforts to discuss the same mechanism of wind-induced coupled vibration for super-large cooling tower working in complex surroundings by means of wind tunnel test. The original mathematical model of the equivalent stastic wind load is supposed to be proposed, taking failure modes and the position of buckling instability into account. The ultimate aim is to present a physical and practical approach for wind-resistant design for super-large cooling towers, as well as the preliminary exploration on wind tunnel test simulate and theoretical model of whole catastrophe process of super-large cooling towers bearing strong dynamic wind load.

我国冷却塔建设日趋高大化（塔高突破世界纪录200m）和复杂化（群塔组合多变，周边构筑物干扰显著），指导结构抗风设计的相关规范缺少与之匹配的等效静力风荷载模型，仅给出165m高度以下单塔、单一风振系数经验值。事实上，超大型冷却塔风振具有多荷载形态、多振型参与和多耦合效应特征，且在复杂环境中其共振和耦合效应愈加突出，相应的等效静力风荷载计算理论及数学模型亟需建立。为此，拟研制可同步测压及测振的冷却塔完备气弹模型，实现从低风速线性振动到高风速失稳破坏试验的全过程，获取并分析考虑自激效应的表面动态风荷载随机特性；建立超大型冷却塔风振耦合作用精细化分析方法，并结合风洞试验揭示复杂环境中超大型冷却塔风振耦合、自激机理；提出具有原创性的考虑多种失效模式和屈曲失稳形态的等效静力风荷载数学模型。最终形成超大型冷却塔抗风设计理论与实用方法，初步探索强风作用下超大型冷却塔动力灾变全过程试验模拟方法和理论模型。

超大型冷却塔属于典型的风敏感结构，我国冷却塔设计规范的风荷载条款仅给出适用于165m高度以下的单塔单一工况风振系数和环向对称风压系数，缺少相应的等效静力风荷载模型和气动抗风措施条款。本项目结合风洞试验、理论推导和数值模拟方法进行了以下三个方面的研究工作：（1）设计制作了可同步测压测振的超大型冷却塔完备气弹模型，进行了典型场地和群塔组合下刚体测压和气弹测振风洞试验，基于试验结果分析了超大型冷却塔表面风荷载随机特性（非高斯、非平稳和时频域特性）和自激力效应。并结合CFD大涡模拟方法，揭示了超大型冷却塔表面风场流动机理和绕流及尾迹特性，建立了基于保证率和相关性的超大型冷却塔极值风压模型，并给出了划分冷却塔表面高斯与非高斯区域的判别标准。（2）基于模态加速度和荷载-响应相关方法提出了能完全考虑背景、共振及两者之间耦合项的超大型冷却塔风振精细化频域计算方法“一致耦合法”，揭示了复杂环境下超大型冷却塔风振自激和耦合作用机理，探讨了特征尺寸、阻尼比和周边干扰对超大型冷却塔风振机理的影响规律，建立了超大型冷却塔结构自身构型和各种可能破坏模式之间的内在联系，进而提出了考虑多种失效模式和屈曲失稳形态的单一和多目标等效静力风荷载数学模型。（3）在此基础上，提出了超大型冷却塔三种典型气动抗风措施（矩形导风板、弧形导风板和外部进水槽），并进行了相应的物理和数值风洞试验模拟，对比研究了不同气动措施对超大型冷却塔表面平均和脉动风荷载、风致响应、局部和整体稳定性及极限承载性能的影响。本项目的试验方法、理论方法和研究成果可为国内外此类超大型冷却塔抗风设计和气动措施选取提供科学参考依据，相关研究成果已成功应用到国内宁夏马莲台电厂超大型冷却塔（170m）、京能盛乐热电厂超大型冷却塔（180m）、内蒙古土右旗电厂超大型冷却塔（210m）、山西介休电厂超大型直筒-锥段型钢结构冷却塔（180m）和陕西彬长电厂特大型冷却塔（210m）等国内重大工程抗风设计，显著改进和完善了我国超大型冷却塔结构抗风设计的可靠性及合理性。研究成果发表期刊及学术论文27篇，其中SCI收录10篇，EI收录15篇，参加国际学术会议1次，国内学术会议3次，申请软件著作权1项。