Assessment of through-wall crack in minimum structures subjected to wave loading

The present paper is an application of fracture mechanics assessment to the analysis of through-wall cracks in minimum structures. Typically the assessment procedure for such a critical structural application, i.e. offshore platforms, has been based on highly computational time consuming processes. The present study proposes the simplified method for assessing the crack tip severity of through-wall cracks in minimum structures. A review of minimum structures and their advantages is presented. Factors affecting the global behaviour of minimum structures are also investigated. The fracture mechanics aspect on the assessment of crack tip severity under cyclic loading condition is explored. In order to get a better understanding of the local behaviour of connections, the 3D-submodel of a through-wall crack pipe is modelled within the full 3D beam element of the brace caisson. The fracture characterizing parameter (CTOD) is extracted from the crack tip region. The applied CTOD results will be compared with those obtained from the simplified method. From the analyses results, it can be seen that the simplified method can enormously reduce the analysis time and allows design engineers to assess the possibility of connection fractures, or determine approximate values of toughness and defect size requirements for given peak stress levels.