Cooling Towers on Flexible Foundations

Abstract

When large cooling towers are placed directly on moderately soft soils or on long piles, the foundation flexibility has a marked influence on tower behavior. Early studies showed that axisymmetric vertical flexibility of the foundations would reduce the capacity of the tower to carry wind loads by the meridional membrane stresses so that the shell would then develop substantial circumferential bending moments over the entire height of the tower. The present paper extends these studies to include nonaxisymmetric foundation stiffness which can arise frequently in practical cases. The method of analysis given here uses a set of soil‐structure interactive equations derived from the principle of virtual work. Displacements and forces are developed by harmonic analysis and the results give the influence of a nonuniform foundation stiffness on the tower behavior. Numerical studies of two typical tower configurations show that, for gravity load it is the variation of foundation stiffness that influences design, while for wind load it is the average uniform foundation stiffness that governs. The method can be used for any axisymmetrical structure.