Naslov
Fractures on a drillship derrick, evaluation and improvement

Autori
Grubišić, Vatroslav ; Barle, Jani ; Vlak, Frane ; Ban, Dario

Izvornik
Engineering failure analysis (1350-6307) 118 (2020); 1-10

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
Life assessment ; Offshore failures ; Weld fatigue ; Finite element analysis ; Fatigue design

Sažetak
During the service life, the drillship derrick structure is exposed to wave and wind actions and drilling operations, with derrick structural member subjected to the variable amplitude stresses and very high number of load cycles that may generate the fatigue cracks, leading to the total structural fracture eventually. To perform the structural durability evaluation and to propose the necessary improvements of derrick footing, the loadings (corresponding loads due to waves, wind and drilling acting on the derrick structure) are defined and taken into account for total drillship service. After that, in order to validate the fatigue life of the structure, the stresses caused by these loads are determined, their representative spectra (cumulative frequency distributions) derived and the data regarding corresponding allowable stresses defined. Using the methods defined in the classification societies' rules and the finite element analysis, the procedure for determination of the operational stress spectra and evaluation of the fatigue life utilising the hot-spot stress approach for highly stressed areas of a drillship derrick, cracked at usage, is presented in this paper.

Izvorni jezik
Engleski

Znanstvena područja
Brodogradnja, Strojarstvo

POVEZANOST RADA