Nonlinear analysis of a RC cooling tower with geometrical imperfections and a technological cut-out

The analysis of nonlinear deformation and ultimate load should be a vital element of the checking-design of cooling towers. This issue is discussed in the paper with respect to an existing cooling tower with large geometrical imperfections and a cut-out made for gas discharge. A brief theoretical background is given, with special attention paid to the finite element model and constitutive relations for reinforced concrete. The numerical analysis deals with three cases: (1) perfect hyperboloid shell of revolution, (2) actual shell with measured geometrical imperfections of the shell mid-surface, (3) imperfect shell with a cut-out. Two types of nonlinearities are considered: (a) material nonlinearity only, (b) material and geometrical nonlinearities. The computations are carried out for a cooling tower shell pinned at the bottom contour. The dead load and wind pressure are applied to the shell. Finite element code Anka is used as the main tool for the numerical analysis. The results of computations for a perfect hyperboloid shell are compared with the results obtained using the DIANA package. It is noted that a considerably softer response corresponds to larger deformations and advanced cracking. The geometrical imperfections only slightly influence the response of the shell. The cut-out introduced into the imperfect shell does not significantly change the shell deformations either.