Wave induced stress profile on a paired column semisubmersible hull formation for column reinforcement

Abstract

A study into reinforcing the hull of the recently developed paired column semisubmersible platform has been carried out by understanding the stress profile around its columns from hydrodynamic interaction during survival and extreme weather conditions in the Gulf of Mexico. The conceptualization of this hull system is to enable dry-tree technology on semisubmersibles for deep-sea exploration. Its hydrodynamic response behaviour has been confirmed to be compatible with this technology, although its size and high steel requirement are of major disadvantage. Preliminary CFD study has showed an unusual flow behaviour within and around the hull due to its unique column arrangement. This behaviour creates an unusual hydrodynamic pressure profile on the hull, dominated by the wave parameters. Numerical models were developed using ANSYS and AQWA to compute the stress distribution on the columns from this unique uneven hydrodynamic pressure. The boundary conditions for the FE-model were formulated using hydrostatic stiffness theories and hydrodynamic response plots developed in Orcaflex. The results have showed high stress concentration on the inner columns. For operating conditions (low wave amplitude), the wave propagating direction was observed to have little or no effect on the column stress distribution. Significant effect of the wave propagating angle was observed as its amplitude gradually increases. Results for topside and deck mass effect on the stress distribution on the columns also suggested high stress distribution around the joint area of the inner columns for extreme and survival weather conditions, irrespective of the flow orientation.

Composite risers for deep waters using a numerical modelling approach

“…Thus, the composite structure becomes lightweight with low bending stiffness. Generally, marine risers are not independent structures, as they depend on other offshore structures like platforms and semisubmersibles (Odijie, Wang, et al 2017;Odijie, Quayle, et al 2017). The behaviour of composite risers in water, as offshore-dependent structures, are subject to environmental loads (Amaechi et al 2018;DNVGL 2017).…”

A review of floating semisubmersible hull systems: Column stabilized unit

“…Matos et al (2011) presented a study of P-52 semisubmersible operating in the GOM. The future recommended semisubmersible hull designs for improved motion behaviour are documented in Odijie et al (2017), Odijie and Ye (2015) and Tan et al (2016).…”

Numerical Assessment on the Dynamic Behaviour of Submarine Hoses Attached to CALM Buoy Configured as Lazy-S under Water Waves

“…The dynamical behaviour of offshore systems attached to a floating offshore platform (FOS) can be investigated using a specialised ocean engineering tool called Orcaflex. Examples are paired-column submersibles (PC Semis) [31][32][33][34][35] and CALM buoys [36][37][38][39]. Orcaflex has also found a notable application in pipeline/hoseline strength assessment [40][41][42] and pipeline installation/laying [43][44][45].…”