Sea state conditions for marine structures' analysis and model tests

Abstract

The study reviews, based on the state-of-the-art findings, some uncertainties associated with wave data and models currently used in design and operation procedures of ship and offshore structures. Although the same basic principles prevail for hydrodynamic loads on ships and offshore structures, actual problems and methods for assessing these loads in the design and operation stage are not the same. Different wave data and models are used for specifying design and operational criteria for these two types of platforms and different uncertainties are related to them. Wave data and models used to define sea state characteristics are discussed and particular attention is given to the associated sources of uncertainties. Some weaknesses of wave input used in design and operational procedures for marine structures are pointed out. Focus is also given on uncertainties related to model tests as tank testing is an important supporting tool for design and operation. Impact of some selected uncertainties on wave description and wave loads is demonstrated by examples. Highlights ► Definitions of uncertainties. ► Establishment of sea state characteristics for marine structures' analysis and model tests. ► Uncertainties associated with sea state characteristics. ► Impact of uncertainties of sea state characteristics on model tests and design and operations of marine structures.

Uncertainties of Estimating Extreme Significant Wave Height for Engineering Applications Depending on the Approach and Fitting Technique—Adriatic Sea Case Study

“…The database was originally obtained as a numerical hindcast performed by the third-generation wave model WAM by ECMWF (European Centre for Medium-Range Weather Forecast) and calibrated with satellite altimetry measurements collected from eight different satellite missions: Geosat (1986)(1987)(1988)(1989), Topex (1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002), Topex/Poseidon (2002)(2003)(2004)(2005), Jason (2002)(2003)(2004)(2005)(2006)(2007)(2008), EnviSat (2002-2010), Geosat Follow-On (2000-2008), Jason-2 (2008-on-going), and Jason-1s (2009-2012) [13,14]. The database represents a state-of-the-art [2], comprehensive, and systematic (in space and time) source of wave data for the offshore Adriatic Sea basin, as it reports twelve different wave and wind physical parameters in 6 h intervals at 39 locations ( Figure 1). Numerically modelled wave data and collected altimetry data joined in a combined dataset were reported with a spatial resolution of 0.5 • × 0.5 • lat./long., starting from September 1992 to January 2016.…”

“…The accurate prediction of these extremes is indispensable for the risk-based design and operation of ships and offshore structures [1]. Bitner-Gregersen et al [2] provided an overview of state-of-the-art in sea state analysis by covering topics from wave data acquisition and wave modelling to the application of results in terms of loading input for ships and offshore structural design. When considering wave loading, it is important to keep track of the associated uncertainties.…”

“…They established a specialists' committee focused on different types of uncertainties. Related research resulted in series of USMOS (Uncertainty Modelling for Ships and Offshore Structures) workshops [2].…”

Uncertainties of Ship Speed Loss Evaluation Under Real Weather Conditions

“…Uncertainties may be classified into two groups: aleatory and epistemic. Related to metocean description, aleatory uncertainty (natural and physic) considers natural randomness of random variable, such as variability of wave intensity in time [7]. This uncertainty is also known as intrinsic or inherent and cannot be reduced or eliminated.…”

Offshore turbines with bottom-fixed or floating substructures

“…Here mainly uncertainties in metocean conditions and soil data are relevant, see e.g. [89], as well as uncertainty in extrapolation methods for extreme events ( [90]). Furthermore, differences of the numerical model to the as-built structure are also an important aspect.…”