Meridional Imperfection in Cooling Tower Design: Update

The effect of meridional imperfection in hyperbolic cooling towers is studied in a continuation of an earlier study by the writers; the present paper takes into account the parallel work performed by Croll, et al. In the previous study the writers assumed the meridional shape of imperfection as the combination of two straight lines. Croll, et al considered the shape to be a combination of circular arcs. In the present study, a general shape is assumed, which becomes the straight line or the circular shape as two extremes depending on the value of a parameter 'C'. Simple expressions for the maximum possible imperfection hoop force and meridional moments are obtained. It is proposed that imperfection stresses be considered explicitly in the design of cooling towers. These stresses can be calculated on the basis of the maximum allowable construction tolerances. The writers suggest further professional discussion to decide whether the designer can lower the apparent factor of safety when the imperfection stresses are explicitly accounted for.