On the Effect of Defect Thickness of ERW Pipe on the Acceptability for Piling Structure

Abstract

A pile is a fundamental part of fixed type platform which commonly used to support superstructure rig in the offshore area. A seamless pipe is usually used as the pile structure. However, this seamless pipe is a high-priced pipe and scarce to find in Indonesia. ERW (Electric Resistant Welded) pipe can be used for an alternative selection of the seamless pipe for piling structure. However, ERW pipe production may have a defect in the form of a cold weld and a hook crack. This paper studies the possibility of ERW pipe utilization as the piling structure. A case study was conducted for ERW pipe NPS 24 and length of 6 m. This research conducted by using eta-FEMB and LS-DYNA software to examine the effective stress of the pile structure during installation. Numerical simulations were carried out on the pile structure with crack modelling and withstand multiple impact loading. The result was compared with failure criterion based on API RP 2A WSD. Those criteria include Axial Allowable Tensile Stress (AATS), Axial Allowable Compressive Stress (AACS) and Critical Hoop Buckling Stress (CHBS). Based on this preliminary analysis, we hypothesize that the ERW pipe with defect length up to 5 mm can be used for the piling structure. However, this analysis need further investigation in order to be a recommendation for substituting seamless pipe for piling structure.