基于结构强健性的台风下200m级特大型冷却塔多尺度破坏机理及设计理论研究

Existing wind-resistant design theories of cooling towers are all based on ultimate limit state under conventional action of good-state wind. It’s difficult for them to explain coupling effect between specific wind profile of mid-scale typhoon and characteristic turbulence of small-scale cooling tower or multiscale failure mechanism of progressive collapse caused by wind-induced local damage; reinforcement of structural robustness is a new idea of existing design theoretical frameworks when effect of violent typhoon is broken through. This project plans to combine macroscopic measured typhoon data to establish a simulation model considering high parameter variability and attenuation effect of real typhoon field. The emphasis will be laid on solving transfer of flow structure, control problem of time scale and trans-scale mutation problem under coupling effect between mid-scale typhoon field and small-scale cooling tower so as to develop a high-precision wind field model of cooling tower coupled by middle/small-scale pattern under a typhoon. Then a multiscale hybrid finite element model of 200m super-large cooling tower was established. CFD/CSD coupling algorithm was combined to investigate multiscale structural failure mode, damage evolution process and energy transfer mechanism during the whole typhoon passing process. On this basis, evaluation indexes of structural robustness and failure probability model were investigated and established based on energy method. Pneumatic measures which could effectively enhance typhoon-resisting capacitance were proposed, and finally design theory of typhoon-resisting robustness of super-large cooling tower with originality was established, which laid a theoretical foundation for performance-based typhoon-resisting design of super-large cooling tower.

现有冷却塔抗风设计理论均基于良态风常规作用极限状态，难于解释中尺度台风特异性风剖面与小尺度冷却塔特征湍流相匹配的耦合效应、以及风致局部损伤导致连续倒塌的多尺度破坏机理；提升结构强健性是突破强台风作用下现有设计理论框架的新思路。本项目拟结合宏观台风实测资料，建立考虑真实台风场参数强变异性和衰减效应的仿真模型，着重解决中尺度台风场与小尺度冷却塔耦合的流动结构传递、时间尺度控制和跨尺度突变问题，发展台风下中/小尺度模式耦合的冷却塔高精度风场模型。然后，建立200m级特大型冷却塔多尺度混合有限元模型，结合CFD/CSD紧耦合算法研究台风过境全过程结构多尺度破坏形态、损伤演化过程和能量传递机理。在此基础上，基于能量法探究并建立结构强健性评价指标和失效概率模型，提出有效增强抗台风承载能力的气动措施，最终建立具有原创性的特大型冷却塔抗台风的强健性设计理论，为基于性能的特大型冷却塔抗台风设计奠定理论基础。

特大型冷却塔作为典型的高耸旋转薄壳构筑物，属于典型的风敏感结构，近年来台风作用下冷却塔结构局部或整体破坏的事件时有发生，考虑中小尺度耦合风场作用下特大型冷却塔结构多尺度破坏机理与强健性设计理论是亟待解决的问题。本项目针对台风近地风特性、台风风压场统计特征及多种台风模型数值模拟结果等进行了统计分析和对比研究，建立了针对台风场参数强变异性和登陆衰减效应的中尺度模式WRF高精度仿真模型，将中尺度台风风场与小尺度冷却塔流场进行耦合，发展了中/小尺度模式耦合下的200m级特大型冷却塔多尺度非线性气弹分析时域紧耦合算法，建立了台风下多尺度模式耦合的特大型冷却塔高精度流场，探究了强台风下200m级特大型冷却塔气动力载荷的时空分布及演化特征。考虑塔筒多尺度壁厚及配筋率变化采用分层壳单元法建立超大型冷却塔多尺度有限元模型，系统开展了220m级特大型冷却塔的非线性强台风致动态响应分析，对比分析了台风和下击暴流典型灾害风环境下特大型冷却塔典型部位多尺度破坏形态和非线性振动特性，探讨了台风和下击暴流风场参数、材料非线性、几何非线性、气弹效应等参数对风致响应的影响机理，并揭示了结构多尺度损伤演化和能量传递机理。基于能量法探究并建立了台风和下击暴流作用下特大型冷却塔结构强健性评价指标和结构失效准则，为此类220m级冷却塔结构的抗特异风理论和结构强健性设计提供理论参考。