A study on deterioration of strength and reliability of aged jacket structures

This paper deals with the deterioration of strength for tubular members with a perforation due to corrosion as a part of reliability-based design of aged jacket structures. Firstly, a simplified method is presented for the residual strength of perforated members subjected to combined compressive load and bending moment by applying the reduced Perry-Robertson's or Carlsen's method. It is also shown that the above estimation results for effects of the perforation on the ultimate strength deterioration are in comparatively good correspondence to analytical results based on nonlinear finite element method using shell elements. Finally, structures are modeled as a spatial framework and reliability analyses are carried out based on collapsing behavior analysis considering the ultimate strength of cylindrical tubular columns with a perforated damage under the combined loads, using a matrix method combined with a plastic node method. These methods are applied to reliability analysis of a 65m-class damaged structure. Aged effects on the deterioration of reliability level of the structure are also demonstrated through numerical examples.