Evaluating Structural Failure in Subsea Equipment: A Comparative Study of API 17G’s 2% Strain Criterion and Strain Energy Methods

Resumo

One of the most commonly used criterion to determine the structural failure of subsea equipment is found in API standard 17G, according to which the collapse takes place if, for any individual component or part, the average equivalent plastic strain in the through section path reaches 2% in the deformed configuration. This is known as "the 2 % strain method". In the present work we investigate alternative methodologies to determine the structural failure of an equipment using approaches based on strain energy. We conduct a series of numerical simulations of structures with prior damaged geometries and determine their structural capacity based on the 2% strain method of API 17G. Those results are used as input for posterior analyses in which the strain energy around the damage is measured (numerically) so we can correlate the ultimate load and the energy absorbed in the vicinity of the damaged area. The results are used for successfully predicting the failure load of different geometries with different damaged areas and a critical discussion is carried out concerning the conservativeness of the API 17G criterion.