DNV GL is an international accredited registrar and classification society headquartered in Høvik, Norway. The company currently has about 14,500 employees and 350 offices operating in more than 100 countries, and provides services for several industries including maritime, renewable energy, oil & gas, electrification, food & beverage and healthcare. It was created in 2013 as a result of a merger between two leading organizations in the field — Det Norske Veritas (Norway) and Germanischer Lloyd (Germany). DNV GL is the world's largest classification society, providing services for 13,175 vessels and mobile offshore units (MOUs) amounting to 265.4 million gt, which represents a global market share of 21%. It is also the largest technical consultancy and supervisory to the global renewable energy (particularly wind, wave, tidal and solar) and oil and gas industry — 65% of the world's offshore pipelines are designed and installed to DNV GL's technical standards. Prior to the merger, both DNV and GL have independently acquired several companies in different sectors, such as Hélimax Energy (Canada), Garrad Hassan (UK), Windtest (Germany) and KEMA (Netherlands), which now contribute to DNV GL's expertise across several industries. In addition to providing services such as technical assessment, certification, risk management and software development, DNV GL also invests heavily in research. Remi Eriksen took over as Group President and CEO of DNV GL on August 1, 2015, succeeding Henrik O. Madsen.
In 2024, Texas operators observed 23-Hz oscillations in real power measurements close to a large electronic load (LEL). Oscillations emerged when the load's power consumption reached approximately 320 MW level and subsided as the active power demand decreased. The paper aims to analyze the event and reproduce the oscillations using electromagnetic transient (EMT) simulations. In the first stage, a representative feedback system is developed, and frequency-domain analysis is conducted to examine the phenomenon and identify its key influencing factors. Next, detailed EMT simulations are performed to further validate the proposed analytical approach. The results show that the feedback system effectively captures and characterizes the critical features of the 23-Hz oscillation incident. In addition, the EMT simulations successfully reproduce the real-world event, with the simulated results closely matching the fault recorder data.
This paper presents a framework for establishing bias factors for combining fatigue damage from two independent stochastic processes considering linear SN-curves. The proposed design approach for calculating fatigue damage consists of identifying appropriate bias factor from bias factor contours pre-generated by simulations, and correcting the linear sum fatigue estimate to account for stress amplification. Depending on input parameters, the approach can account for Gaussian, non-Gaussian, wide-banded and narrow-banded processes in a practical way, which is not achieved by existing methods. For long-term fatigue assessments, simplified approaches are possible by selecting a conservative representative bias factor at global minimum, while more accurate estimates can be found by more careful selection of bias factor per short-term condition. Case-specific design contours tailored to the application can be generated using the methodology described. In this paper examples of design contours for combination of wave induced-and vortex induced vibrations (VIV) fatigue relevant for marine risers are presented.
Modern simulation and analysis tools rely on assumptions and numerical schemes that inevitably affect their outputs, leading to uncertainties and biases that must be quantified and bounded, especially when they influence critical aspects such as system stability. This paper presents recent results from an aeroelastic benchmark on a reference 15-MW wind turbine, conducted by multiple partners within the framework of the International Energy Agency (IEA) Wind TCP Task 47 TURBINIA, focusing on stability characteristics and aeroelastic responses. The agreement among the results is reasonably good, although some quantities exhibit a significant spread. This is particularly evident in the damping factors of the turbine modes and in the periodic loads observed under sheared conditions.
Concern for the collapse behaviour of ships and offshore structures and their structural components under ultimate conditions. Uncertainties in strength assessment shall be highlighted. Attention shall be given to the influence of load combinations, fabrication-induced imperfections, life-cycle effects, damage, and user approach. Consideration shall be given to the practical application of methods.
