Finite Element Assessment of Thin Shell Structures

A geometrically and physically nonlinear finite element model for thin reinforced concrete shells is presented which allows simulation of the deformation history of imperfect structures up to their numerical failure. Application to the assessment of existing natural draught cooling tower shells subjected to dead weight and wind loading demonstrates the usefulness of the numerical procedure. Results showed that failure was due to a nonlinear stress problem, rather than elastic buckling. For worst-case imperfections relating to the physically nonlinear failure mode, the shells exhibited only a moderate imperfection sensitivity. Further work will concentrate on more realistic imperfection patterns, since worst-case imperfections give a rather too conservative lower bound for the collapse loads.