Optimum analysis of offshore structures lifting padeyes using finite element method

Abstract

Padeye design and analysis plays an important roles during the lifting, load out and installation of heavy structures. This study addressed the different dynamic amplification factors that are adapted in the oil and gas industry based on different design codes. This study explains the impact of limiting the effective thickness of the cheek plate with respect to the main plate of the padeye and the advantages of increasing the effective thickness of the cheek plates. It also touched on the fabrication requirements to achieve the required effective thickness of the cheek plates. In addition, a sensitivity study about the impact of the out of plane force on the padeye design is addressed and the maximum out of plane angle that shall be considered is recommended. A finite element analysis using London University Structure Analysis System (LUSAS), is conducted and compared with the hand calculation. The benefits and advantage of using FE analysis is addressed in this study. At the end of this research a guideline on the design of the padeye is developed. It has been found that the dynamic amplification factor can be reduced to a lower value of 1.15 instead of 1.35. The effective thickness of the cheek plate can be increased to 100% with proper fabrication and welding sequence. Finite Element analysis is a good tool to have better analysis and design of the lifting padeyes.