Operability Analysis of the Vibratory Extraction Process of an Offshore Monopile Foundation Using a Crane Barge

Abstract

Analysis of the operability under environmental uncertainty is important for on-board decision-making and will impact the safety and economy of complex marine operations. To this end, this study examines the operability of a crane barge during the vibratory extraction of a monopile foundation. A numerical model has been developed to couple the dynamic behavior of the monopile with that of the crane barge during vibratory monopile extraction. The model incorporates the centrifugal force generated by the vibro-hammer and the reduced soil resistance caused by cyclic loading, implemented via the external dynamic link library. This model is used in the present study to conduct operability analysis. The dynamic response of the coupled system is analyzed by investigating the effects of modeling the vibro-hammer mass as either a distributed mass or a lumped mass. An extreme value analysis is conducted to evaluate the operability of the crane barge and establish the allowable sea states for safe operation. The findings reveal that the modeled crane barge exhibits low operability in the examined zone, primarily due to its limited freeboard, large weight of the monopile and vibro-hammer, and the harsh environmental conditions of the considered site.