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Oslo, Norway

DNV GL is an international classification society, with main locations in Norway and Germany. DNV GL is the result of the 2013 merger between DNV and Germanischer Lloyd. Wikipedia.


McGeorge D.,DNV GL
Engineering Fracture Mechanics | Year: 2010

Adhesive bonding offers a simple and efficient way of joining structural components without weakening them by holes or welding. This article develops a new model to predict the fracture load of bonded overlap joints using a fracture mechanics approach. The bondline fracture resistance and effects of the nonlinear inelastic behaviour of structural adhesives are accounted for separately. For bonded single overlap joint configurations the model is expressed as simple explicit formulas. An experimental programme is presented where the design parameters that a designer can adjust to obtain the desired joint capacity are systematically varied. Comparison of test results with the predictions by current strength-of-materials capacity models highlights disparities between the theoretical predictions and experimental evidence. In contrast, the new model shows good agreement with the experimental results. It should be noted that the simple new formulas apply to a well-defined range of bonded overlap joint configurations and do not purport to apply in general to every other joint configuration. © 2009. Source


Bitner-Gregersen E.M.,DNV GL
Applied Ocean Research | Year: 2015

For several engineering applications, joint met-ocean probabilities are required. Recently increasing attentions have been given to importance of inclusion wind-sea and swell components in the joint description. Presence of wind-sea and swell will affect design and operability of fixed and floating offshore structures as well as LNG terminals. The study presents a joint met-ocean model which can be applied for design and operations of marine structures, including LNG platforms. The model is fitted to hindcast data from four locations: Southern North Sea, West Shetland, and Northwest Shelf of Australia and off coast of Nigeria. Uncertainties related to the proposed fits are examined focusing on location specific features of the wave climate and an adopted partitioning procedure for the wave components. Implications of the uncertainties on design and operation criteria of LNG platforms are discussed and demonstrated by examples. © 2015 Elsevier Ltd. Source


Saasen A.,DNV GL
Journal of Energy Resources Technology, Transactions of the ASME | Year: 2014

Controlling the annular frictional pressure losses is important in order to drill safely with overpressure without fracturing the formation. To predict these pressure losses, however, is not straightforward. First of all, the pressure losses depend on the annulus eccentricity. Moving the drillstring to the wall generates a wider flow channel in part of the annulus which reduces the frictional pressure losses significantly. The drillstring motion itself also affects the pressure loss significantly. The drillstring rotation, even for fairly small rotation rates, creates unstable flow and sometimes turbulence in the annulus even without axial flow. Transversal motion of the drillstring creates vortices that destabilize the flow. Consequently, the annular frictional pressure loss is increased even though the drilling fluid becomes thinner because of added shear rate. Naturally, the rheological properties of the drilling fluid play an important role. These rheological properties include more properties than the viscosity as measured by API procedures. It is impossible to use the same frictional pressure loss model for water based and oil based drilling fluids even if their viscosity profile is equal because of the different ways these fluids build viscosity. Water based drilling fluids are normally constructed as a polymer solution while the oil based are combinations of emulsions and dispersions. Furthermore, within both water based and oil based drilling fluids there are functional differences. These differences may be sufficiently large to require different models for two water based drilling fluids built with different types of polymers. In addition to these phenomena washouts and tool joints will create localised pressure losses. These localised pressure losses will again be coupled with the rheological properties of the drilling fluids. In this paper, all the above mentioned phenomena and their consequences for annular pressure losses will be discussed in detail. North Sea field data is used as an example. It is not straightforward to build general annular pressure loss models. This argument is based on flow stability analysis and the consequences of using drilling fluids with different rheological properties. These different rheological properties include shear dependent viscosity, elongational viscosity and other viscoelastic properties. © 2014 by ASME. Source


Goldberg M.,DNV GL
IEEE Power and Energy Magazine | Year: 2010

DEMAND RESPONSE (DR), IN BROAD TERMS, IS A CHANGE IN ELECTRICITY USE by end-use customers within a day or less in response to some type of incentive or price signal. Measurement and evaluation are important for DR operations and improvement. © 2006 IEEE. Source


Over the last 30 years it has become standard practice to connect offshore oil and gas structures to their foundation piles using cylindrical shaped grouted connections with shear keys or weld beads. Circumferential shear keys, or weld beads, are provided around the outside of the piles and the inside of the pile sleeves in jacket structures to transfer forces through the grouted connection. The same methodology is also now being used by the wind energy industry to connect wind turbine support structures to their foundation piles. These structures are subjected to rather severe dynamic loading, it is therefore important to document the fatigue capacity of these grouted connections. As a direct result of this need, a joint industry project focusing on the capacity of cylindrical shaped grouted connections with shear keys was initiated by DNV in January 2011 and continued through until completion in May 2012. This project has involved fatigue testing of grouted test specimens in the laboratory, finite element analyses and assessment and development of a recommended design methodology. The design methodology includes the Ultimate Limit State and the Fatigue Limit State. Fatigue testing of full-scale specimens would require very large test setup and hydraulic actuators. Therefore special box specimens were designed with a representative radial stiffness similar to that of large diameter connections, with both full size grout thickness and geometry of the shear keys. An analytical approach for design of these specimens and for the design of grouted connections in monopiles is presented in this paper. © 2013 Elsevier Ltd. Source

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