Methodology for the structural analysis of a main deck of FPSO vessel supporting an offshore crane

Abstract

Offshore cranes placed on the surface of Floating Production Storage and Offloading (FPSO) vessels affect the structural response of their main decks, which can alter the safe operation of the FPSO vessels. Generally, classification societies rules are used to predict the structural strength of the main deck of FPSO vessels. However, these classification societies rules are limited to estimate the variation of the structural performance of the main deck caused by the operation of offshore cranes under different hydrodynamic conditions. Here, we present a methodology to determine the alteration of the structural behavior of a main deck of FPSO vessel due to different operation conditions of a board offshore crane. This methodology considers the hydrodynamic response for two ultimate limit states: operating and storm conditions from 1000 m water depth in Gulf of Mexico with a return period of 10 and 100 years, respectively. The methodology includes finite element method (FEM) models of the main deck supporting an offshore crane to predict its structural response. The maximum von Mises stress of the main deck does not overcome its maximum permissible stress, which allows a safe operation of the FPSO crane. The proposed methodology can be used to estimate the structural behavior of main decks of FPSO vessels that are modified for supporting offshore cranes, regarding the hydrodynamic response for each FPSO under the operation and extreme conditions in its location. Thus, naval designers could select the better structural modifications of the main decks that decrease their costs of construction and maintenance.

A Methodology to Assess the Sloshing Effect of Fluid Storage Tanks on the Global Response of FLNG Vessels

“…where M is the mass, B is the damping and K is the hydrostatic stiffness coefficient of the ship, and f(t) is the function of external environmental force. By using the frequency domain with 2 / K M   , the following constant C is used to predict the RAOs [2]:…”

“…where F is the magnitude of force, ω R is the excitation angular frequency, ω is the natural angular frequency, β is the damping factor, and i the imaginary unit. The Pierson-Moskowitz (PM) wave spectra (S PM ω ) are studied by using the environmental contours of the location [2] with a return time of 100 years, which describes the sea state conditions at the specific location (hypothetically).…”

“…However, this sloshing phenomenon should also be studied if the vessel is modified to move other fluid cargo types. For the design and operation of an FLNG vessel, the naval designers must investigate the sloshing effect of the internal fluid in the tanks on the global motion response and the vessel's structural behavior in order to ensure the safe performance of the vessel under different operating and extreme environmental conditions [2][3][4][5].…”

Structural Analysis of Deck Reinforcement on Composite Yacht for Crane Installation

“…Its hull structure was made of sandwich construction with carbon/epoxy composite face sheets and polyvinyl chloride (PVC) foam core [6]. Hernández-Ménez et al introduced a methodology utilizing FEM to predict the structural response of a deck supporting an offshore crane [7]. FEM has also been utilized for the evaluation of performance for speed vessels (small crafts) made by aluminum [8].…”

Structural analysis of a slotted flap redesigned with composite materia

“…Their versatility, robustness, and computational efficiency make them well suited for the real-time, largescale aircrafts, structures, and habitat applications [8], [9]. One of the most widely utilized numerical techniques is the finite element method (FEM), which allows to adequately represent the stresses and strains that occur in mechanical components [11], [12], characterize complex material behavior [13], and it is suitable for complex geometries such as that of the flaps [14]. With the results of the simulation, it is possible to identify the critical points in the design of the components and if the selected material would have the right properties for manufacturing these parts [15].…”