No abstract

This paper presents the experimental test results for the buckling capacity of tubular columns exposed to simulated unsymmetrical patch corrosion damage. These tests were performed to investigate how the results of these experiments compare with the capacities obtained for the formulae provided in the 2004 revision of NORSOK N-004. Formulae for patch corroded tubular columns are needed in standards and as such it is unfortunate that these formulae are removed from the present revision of the NORSOK N-004 standard. Prior to suggesting introducing these previous formulae in standards, experimental tests to confirm good correlation between experiments and formulae are needed. The tests performed in this work are presented in this paper for 100% (intact columns), 69%, 34% and 0% remaining wall thickness in the patch.

Daewoo Shipbuilding & Marine Engineering Co., Ltd. (DSME), StatoilHydro and DNV established a common project to investigate the reason for the difference between calculated fatigue lives and the in-service experience and to assess the fatigue capacity of stiffener web connections subjected mainly to web frame shear stresses. The main objective of the work was to establish fatigue test data and perform numerical analysis of collar plate connections in order to provide improved confidence in analysis methodology for fatigue life assessment. Large scale fatigue tests of different types of connections were carried out to obtain fatigue test data of collar plate connections. Finite element analyses were carried out for comparison with fatigue test data and with measured stresses on the test model. Based on this work recommendations on fatigue design analysis of connections between stiffeners and web frames have been derived. The background for this is presented in this paper.

A methodology to calculate the fatigue damage in non-collinear wind generated sea and swell has been proposed for weather vaning turret moored FPSO’s. The methodology consists in specifying long-term distributions of sea and swell conditions by directional wave scatter diagrams of Hs and Tp and extracting the swell – and wind wave contributions by use of the Torsethaugen double-peaked wave spectra. By assuming the wind sea induced response and the swell induced response to be independent narrow banded processes, response spectra for the combined processes are established. The wave loads are calculated from a hydrodynamic analysis and a closed form approach is used to calculate the fatigue damage summation. The fatigue damage of selected side longitudinal stiffener fillet welds is calculated by using the proposed methodology for a Norwegian Sea FPSO at three different hull girder cross-sections. The relative contributions from sea and swell to the total damage are identified as well as the sea-states and headings that contribute most to the total damage. In addition, the proposed methodology is compared with the more traditional approach, assuming both wind sea and swell to come from the same direction. For the traditional approach, the corresponding resulting wave spectrum used is a single peaked type, i.e. Pierson Moskowitz.

No abstract