双曲冷却塔温度效应分析

Study on the thermal effects of hyperboloidal cooling towers

以某大型冷却塔为例,通过与自重和风荷载作用效应的对比和荷载效应组合,分析了温度效应对结构设计的影响,并对比了中、英、德3国规范温度效应的相关条款和构造要求.结果表明:初始温度对温度效应基本没有影响,但檐口和下支柱等端部构件温度荷载参数的缺失使塔筒上下端形成温度边界约束,致使本区域构件的内力急剧增加;环向弯矩同样是结构设计中的控制性内力,并且温度效应对环向弯矩的贡献一般要显著大于风载荷效应的;相比英、德规范,我国规范的环向最小配筋率明显偏低,为保证环向强度安全,须通过结构计算而不能简单采用构造配筋,故有必要适当提高环向最小配筋率.

Researches were initiated for the hyperboloidal cooling towers. Based on the comparisons and combinations with dead weight effects and wind effects, the functions of thermal effects for struc- ture design were elaborated. Related specifications and detailing requirements in China, British, Ger- many codes were compared as well. Results show that the initial temperature of cooling tower shells hardly have influences on the thermal effects, and the huge illogical internal forces in top and bottom edge shells are due to the missing of temperature parameters of cornice and columns which give rise to a temperature constrain condition. The circumferential moment is also a controlling internal force in structure design, and the contribution from thermal effects is much bigger than that from wind effects. Compared with British and Germany codes, the minimum circumferential reinforcement in China code is much smaller, the strength safety must be satisfied according to structure analysis but not only constructed reinforcement, the minimum reinforcement ratio should he increased.