Structural resistance safety level in Eurocode versus NORSOK and ISO

Abstract

The objective of this thesis is to analyze and compare the capacity limits, hence the inherent safety level for the actual structure, using various standards and regulations such as Eurocode, NORSOK and ISO. The main tool for the analyses is DNV’s software SESAM: Genie, which is used for modeling and code check of the structures.

All the three codes adopt the same design approach, namely the Load and Resistance Factor Design (LRFD). The analysis of the formulas for the three design standards shows that the standards are similar in the way that they provide formulae for load effects acting alone and in combination. The analysis of the formulas in the parameter studies shows significant differences in the capacity between Eurocode and NORSOK/ISO and in the partial factors for the design. The design formulas for NORSOK and ISO are identical and the differences in design results are entirely due to the differences in the partial factors.

In addition to the parameter studies, two case studies are performed for a redesigned topside module consisting of tubular cross sections. The first case study was performed using the resistance and action factors according to the design standards, whereas the second case was carried out based on the resistance factors and action factors according to NORSOK. The results of the analysis identified significant differences between the design codes, with Eurocode to be the most conservative approach for most of the cases.