Cylindrical ring-stiffened fluid containers - critical wind loads during the erection

The presented paper deals with the occurrence of critical load conditions due to wind loads during the erection of cylindrical ring-stiffened fluid containers in steel. Particular attention is drawn to fluid containers with stepwise tapered wall thickness under construction, wherein the upper circumferential edge of the cylindrical shell is not yet constraint by the roof structure. In some cases the verification of structural safety according to national standards (DIN 18800-4), based on a simplified design procedure, cannot be provided. According to European standards, the characteristic values for wind speeds may be reduced on the basis of the time duration of the specific erection phase and in the case that additional securing of the structure is possible. Realistic buckling resistance values for the single erection phases of a major size storage tank are obtained through a finite element analysis, taking account of a realistic circumferential wind load distribution and geometrical imperfections. By virtue of probabilistic considerations applied to the deterministic results of the FEM model, the actual structural safety of the tank during a specific erection phase can be expressed as a function of the time duration of the latter.