大型冷却塔结构多目标等效静风荷载分析

Multi-Objective Equivalent Static Wind Loading for Large Cooling Towers

大型冷却塔属于典型的风敏感结构,针对其风振响应的多耦合效应、多振型参与和多目标等效的特点,以冷却塔表面平均风荷载和主导振型的惯性风荷载作为构造多目标等效静风荷载的2个基本向量,并结合约束最小二乘法,得到基本向量的最优组合系数,从而获得针对多个等效目标的等效静风荷载。该方法的优点是:建立了更符合实际分布的等效风荷载,限制了某些奇异荷载作用模式的出现,能够再现风振响应特点。结合某核电站大型冷却塔结构的风洞试验,对3组不同等效目标的结构响应进行了多目标等效静风荷载分析,结果表明在该方法得到的多目标等效静力风荷载作用下的风振响应与极值响应吻合较好。

Large cooling towers are the typical wind sensitive structures. According to the characteristics of multiple coupling effect of wind induced responses, multimode and multiple equivalent objectives, mean wind loads and dominating vibration modes were selected as the basic vectors to express equivalent static wind loads for multiple objectives, and a constrained least squares method was applied for calculating the optimal combination factors of these basic vectors, in order to obtain multi-objective equivalent static wind loading. The advantage of the method is that equivalent static wind loads could reduce the dimension of equivalent static wind loading vector and to exclude some unrealistic and curious load distributions, and reflect the characteristics of wind-induced response. Combined with a wind tunnel test of large cooling towers in a nuclear power plant, the multi-objective equivalent static wind loading was analyzed for three groups of different equivalent targets＇ structural response. The results show that the wind induced response under multi-objective equivalent static wind loading agrees well with the peak values under the actual dynamic wind loads.