Stability of super-large cooling tower under winds during construction considering structure-pile-soil interaction

Local instability is one of the most common forms of wind-induced failure of super-large cooling towers. Current codes and research methods often neglect the coupling effect among the superstructure, pile, and soil, particularly during the long-term construction process. This makes it challenging to accurately predict the wind resistance of such structures. Taking a coastal super-large cooling tower as the research object, an integrated finite element model considering the whole construction process and interaction among the superstructure, pile foundation, and soil was developed. The surface wind pressure on the cooling tower was derived from wind tunnel rigid pressure measurement and the code K1.2 curve. Nonlinear stability analyses under strong wind were performed for the structure-pile-soil coupling model and the base-fixed model. This study systematically compared differences in the buckling coefficients and buckling displacements of the cooling tower during the whole construction process, considering concrete age, construction loads, material and geometric nonlinearities, and internal suction effect. The influence of structure-pile-soil interaction on the buckling stability of cooling towers was revealed, and an engineering empirical formula was proposed to evaluate the relationship between buckling coefficients and construction progress. The results indicate that considering structure-pile-soil interaction reduces the fundamental frequency of the super large cooling tower by 18.78%, decreasing the local stability coefficient at the tower body, but increasing it at the tower top. Considering concrete age, construction loads, and internal suction effect lead to reduced buckling stability of the cooling tower, which is further weakened by the coupling effect. The most unfavorable condition for the buckling coefficient occurs when both structure-pile-soil coupling and internal suction effect are considered simultaneously. Similarly, the most unfavorable condition for buckling displacement occurs when pile-soil coupling, concrete age, and construction loads are jointly considered. The proposed empirical formula demonstrates high reliability and stability, providing a scientific basis and practical reference for the preliminary evaluation of the variation of buckling coefficients with construction conditions.