Original scientific paper
Procedure for the Service Strength Approval of the Drillship Derrick
Vatroslav V. Grubišić
; Croatian Academy of Sciences and Arts, Zagreb, Croatia
Jani Barle
; Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture (FESB), University of Split, Split, Hrvatska
Abstract
Service strength approval of a drillship derrick must include beside the static strength validation under limit loads, also the fatigue evaluation for the critical areas of the derrick structure. During the service life structural members of the derrick are exposed to giga stress cycles with variable values, caused by wave and wind action and drilling operation. These variable stresses can generate the fatigue cracks and lead to the total fracture of the structure. For the fatigue strength evaluation of a drillship derrick is important to define the loading taking into account the drillship usage. To determine the loading it is necessary to evaluate the ship motion and to calculate the corresponding loads due to waves, wind and drilling operation acting on the derrick structure. For the fatigue life validation, the resulting stresses, caused by these loads must be determined and their representative spectra (cumulative frequency distributions) derived.
In this paper the procedure to determine the operational stress spectra and to evaluate the fatigue life of a drillship derrick is described.
Keywords
Operational loading; Stress spectra; Drillship derrick; Service strength; Fatigue life estimation
Hrčak ID:
141356
URI
Publication date:
14.7.2015.
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