双曲壳结构非均匀风压作用局部稳定验算

LOCAL STABILITY ALGORITHM FOR HYPERBOLIC SHELL STRUCTURES UNDER NON-UNIFORM WIND LOADS

风荷载条件大型双曲旋转壳体结构局部稳定性为结构设计关键控制因素。为考虑双曲旋转壳体结构在风载荷作用下的局部稳定性问题,现行国内外水工规范多采用20世纪70年代提出的基于环向均匀荷载加载试验方案的Mungan局部稳定验算公式(亦称为Buckling Stress State (BSS)方法)。首先,以Mungan提出的静水压力试验为基础,基于结构有限元分析算法,构建了早期壳体物理试验模型的有限元模型,分析了双曲旋转壳体在环向均布平均风压作用下的稳定性与试验结果的差异,验证了早期试验在特定条件下的正确性。为进一步评价该算法应用于以超大型冷却塔为代表的壳体结构设计的适用性和合理性,计算了水工规范(GB/T 50102―2003)中21种线型的双曲旋转壳体在环向非均布风压作用下的极限荷载,探讨了Mungan局部稳定验算公式有待改进的方向,提出了适用于非均布荷载作用下环向应力临界荷载计算公式,拟合得到改进的局部稳定验算公式。研究表明:水工规范建议的双曲旋转壳体结构局部稳定验算公式难于描述壳体实际情况下的非均布风压变化受力特征,推荐适用于非均匀风压分布变化的更新局部稳定验算公式,可以兼顾结构设计过程的便捷性与合理性。

The stability of large-scale hyperbolic shells under wind loads is one of key control factors during structural design. In order to evaluate the local stability of hyperbolic shell structures under the combined action of wind load and other loads, the current codes usually adopt the local stability check formula proposed by Mungan, based on the stress-measured model test considering uniform hydrostatic pressure in 1970 s, which also known as Buckling Stress State(BSS) approach. In order to investigate the applicability and rationality of the algorithm while facing to the current development of super-large cooling towers. Based on the structural finite element method, the revisiting analysis aiming at earlier physical models was conducted to validate the existing stability check formula. Then series of calculations involving 21 types of hyperbolic shell cooling tower structures were implemented to clarify the difference between the circumferential fluctuating wind pressure distribution and the uniform pressure distribution of wind-induced internal forces. Under the condition of the wind pressure ultimate load, an updated formula for the critical circumferential stress is proposed. Furthermore, the updated local stability check formula is fitted for engineering practice. The investigation shows that the existing local stability formula of the hyperbolic shell structure from various loading codes cannot deal with 3 D non-uniform wind pressure actions. It is recommended to use the updated formula to account complex wind load distributions.