The present work aims at modelling the collapse mechanisms and the related limit loads of thin R.C. shells. A numerical approach is developed, in order to model both the buckling and the bending collapse mechanisms within the framework of the finite element technique. The mechanical behaviour of R.C. is modelled with an elasto-plastic-fracturing formulation including a special tension-stiffening approach along with a smeared cracks mode. Doubly curved elements are used in order to describe the shape of the shell. The proposed method of modelling is applied to an R.C. shell of large span and small thickness. Results provided by the model are compared with observed response quantities, and the accuracy as well as the efficiency of the model are proved. The actual safety margin of the reference shell, represented by the collapse load multipliers and the related mechanisms, are assessed before and after its rehabilitation.
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