DNV GL

About: DNV GL is a company organization based out in Sandvika, Norway. It is known for research contribution in the topics: Corrosion & Finite element method. The organization has 1929 authors who have published 2387 publications receiving 34644 citations.

Bend Stiffener Design for Umbilicals

Abstract: A crucial design issue for compliant risers and umbilicals for dynamic applications is termination of the compliant structure to a rigid structure. A practical way to solve this problem is to introduce a properly designed bend stiffener to limit the stresses in the compliant structure due to bending at the supports. The bend stiffener provides a gradually increase of the bending stiffness from the rather small value of the compliant structure to a significantly larger value that can be rigidly connected without compromising the structural integrity of the compliant structure. Hence, the bend stiffener geometry needs to be designed to fulfill the design requirements for extreme as well as fatigue loading conditions for the compliant structure. Furthermore, it is required that the bend stiffener is as short as possible to limit costs, support forces, and enable fabrication and installation. The main focus of this paper is to outline an optimization scheme for bend stiffeners to meet design criteria for extreme loading conditions. Measures to provide an adequate fatigue performance of bend stiffeners are also discussed. The loads on the bend stiffener are governed by effective tension and relative angle close to the support (i.e. direction of effective tension relative to the longitudinal direction of the compliant structure at the support). Combinations of effective tension and relative angle aggregated for all relevant extreme load conditions define the design loads on the bend stiffener. The capacity of the compliant structure is governed by a capacity curve expressing the allowable curvature as function of the effective tension. A general optimization scheme is outlined accounting for a general description of the design loads as well as the capacity curve. The optimization methodology is based on a general purpose optimization algorithm utilizing a tailor made non-linear static finite element solver to describe the response of the bend stiffener and the compliant structure. Non-dimensional design curves are also presented based on a simplified conservative description of the design loads and the capacity. This allows for easy practical sizing of bend stiffeners without the need for sophisticated optimization software.Copyright © 2011 by ASME

Airgap Prediction" Use of Second-Order Diffraction And Multi-Column Models

Abstract: The airgap of a specific semi-submersible platform subjected to irregular waves is considered. The effects of including second-order diffraction contributions are demonstrated, and the sensitivity of this analysis to numerical model complexity is investigated. Detailed model test results for both motions and airgap time histories are used to verify the analysis results. A new approach is proposed for use in post-processing secondorder hydrodynamic transfer functions. In the new approach, those transfer functions that are unavailable or believed to be unreliable are replaced with those of an undisturbed second-order Stokes wave. Results of detailed hydrodynamic analysis are also compared with those from a simpler numerical method, which uses a multi-column model of the semi-submersible platform to compute the diagonal of the quadratic transfer function matrix. To use the results from this simpler model, another new approach to extrapolating hydrodynamic analysis results is proposed: unknown off-diagonal terms of the quadratic transfer function matrix are estimated from the known on-diagonal terms. The results of each analysis are critically compared. The overall goal is to demonstrate the numerical impact of: 1) performing a very detailed second-order diffraction analysis, 2) performing a simplified secondorder diffraction analysis, or 3) ignoring second-order diffraction entirely.

Information governance as a basis for cross-sector e-services in public administration

Abstract: Information governance and systematic work with metadata and semantics are important elements of the implementation of an open, transparent, accessible, accountable, user-friendly and service-oriented public sector. Top management commitment is crucial in order to achieve necessary attention and sufficient budgets. Management needs to be aware of metadata and semantics as important enablers for the goals set forth in strategies and requirements from ministries. Documentation of economic potential and cost savings will help to get attention among decision makers, but today, few trustworthy sources are available. The development of cross-sector services and the demand for reuse of public service information, both in the public sector itself, but also for commercial services, underpins the importance of well-defined information. Participation in cross-sector e-Services demands the establishment of metadata repositories and ontologies as obligatory parts of the public sector information governance regimes.