STRUCTURAL MONITORING AND NUMERICAL-ANALYSIS OF THE WIND RESPONSE OF OLD COOLING-TOWERS

The paper presents the first results of an ongoing joint research proj ect on structural behaviour of RC cooling towers, especially focused o n the response to wind loading. As a matter of fact, several Italian c ooling towers have been built in the fifties and are now showing evide nt signs of ageing. The attention must now be devoted to behaviour con trol and estimate of extreme loading conditions in order to identify s ome guidelines for a careful strategy of monitoring, maintenance and s trengthening. In the first part, the paper refers to some experimental activities carried out by ENEL-CRIS which have concerned with one of the cooling towers of ENEL's S. Barbara power plant. This has been ins trumented in order to evaluate the seasonal evolution of the thermal l oads and the temperature effects. Accurate analyses were performed, wh ich explained the main sources of the deterioration process. The secon d part is devoted to a comparative analysis among several wind loading assumptions, which is based on numerical simulations of the structura l response and referred to a typical RC cooling tower geometry used by ENEL in the fifties. Static wind loading has been considered followin g the assumptions of several European codes. A possible approach to th e shell strengthening has been finally checked. This consists in remov ing part of the shell thickness and reinforcement and substituting it with new materials, moving from the top of the tower and proceeding do wnwards in annular strips of given height. A special attention has bee n given here to the problem of overall buckling.