Study on Bearing Capacity of Offshore Derrick with Pitting Corrosion Based on Multi-Scale Simulation

Corrosion damage is a vital factor that causes strength weakening or even failure of offshore derrick. To study the influence of local corrosion on the derrick, a regular spherical pitting model was adopted to analyze the evolution mode of pitting corrosion damage and the corresponding pitting corrosion damage models with different morphology. The connection technique for the across-scale interface was discussed, a method for constructing multi-scale models of derrick with pitting corrosion damage was proposed. The pitting damage simulation and ultimate bearing capacity analysis are carried out for an offshore derrick in service. The results show that the interaction between meso-scale pitting corrosion damage and macro-scale structure can be effectively considered, the stress distribution of the pitting corrosion damage and its effect on stress concentration coefficient can be obtained, and the influence of local random pitting distribution location, style, and density on the ultimate bearing capacity can be determined. In addition, the ultimate bearing capacity can be predicted. It provides a new idea for bearing capacity prediction and safety assessment of large steel frame structures in service with local damage.