SAFETY FORMAT AND ACCEPTANCE CRITERIA FOR ANALYSIS OF MARINE STRUCTURES USING NON-LINEAR METHODS

This paper deals with how structural integrity can be documented by use of non-linear analysis methods. The focus is on structures that are exposed to extreme environmental loads. In order to prove the structural integrity for aging offshore installation, non-linear analysis methods are finding increased applications. The codes ISO 19902, API RP 2A and Norsok N-006 give recommendations for use of non-linear methods for capacity checks of existing structures. This paper discusses the different safety formats given in these codes. Also presented is how practical acceptance criteria that have to be applied in conjunction with such analyses can be formulated. The topics that are dealt with are issues that the analyst performing such analyses needs to address like: definition of failure, representation of joints, issues on cyclic loading, instability of cross sections and member buckling. In cases of novel design solutions or special structural details, non-linear analysis methods may also find application when planning new structures.