Blar i NTNU Open på forfatter "Schafhirt, Sebastian"
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Alternative Numerical Pile Foundation Models for Integrated Analyses of Monopile-based Offshore Wind Turbines
Page, Ana M.; Schafhirt, Sebastian; Eiksund, Gudmund Reidar; Skau, Kristoffer Skjolden; Jostad, Hans Petter; Sturm, Hendrik (Chapter, 2016)Lowering the cost for offshore wind energy remains a major challenge. Increasing the accuracy of analysis tools used in the design and optimization process can strengthen the reliability and reduce conservatism, thereby ... -
Characterization of wave slamming forces for a truss structure within the framework of the WaveSlam project
Rausa Heredia, Ignacio Eugenio (Master thesis, 2014)The foundations of offshore wind turbines in shallow water are predominantly truss structures which are exposed to wave slamming forces. In these situations the design of the structure is governed by high and rapid impacts ... -
Comparison of different approaches to load calculation for the OWEC Quattropod jacket support structure
Zwick, Daniel; Schafhirt, Sebastian; Brommundt, Matthias; Muskulus, Michael; Narasimhan, S; Mechineau, Jonathan; Haugsøen, Per (Journal article; Peer reviewed, 2014)Accurate load simulations are necessary in order to design cost-efficient support structures for offshore wind turbines. Due to software limitations and confidentiality issues, support structures are often designed with ... -
Decoupled simulations of offshore wind turbines with reduced rotor loads and aerodynamic damping
Schafhirt, Sebastian; Muskulus, Michael (Journal article; Peer reviewed, 2018)Abstract. Decoupled load simulations are a computationally efficient method to perform a dynamic analysis of an offshore wind turbine. Modelling the dynamic interactions between rotor and support structure, especially the ... -
Dynamic Analysis and Structural Optimization of Support Structures for bottom-fixed Offshore Wind Turbines
Schafhirt, Sebastian (Doctoral theses at NTNU ;2017:363, Doctoral thesis, 2017)Wind energy is recognized as a reliable and affordable source of energy for generating electricity. Up to date most of the wind energy capacity is installed onshore, but legal regulations and a shortage of potential locations ... -
Effect of Load Sequence and Weather Seasonality on Fatigue Crack Growth for Monopile-based Offshore Wind Turbines
Ziegler, Lisa Sabine; Schafhirt, Sebastian; Scheu, Matti Niclas; Muskulus, Michael (Journal article; Peer reviewed, 2016)Offshore wind turbines are subjected to variable amplitude loading, but the impact of load sequence is commonly neglected in fatigue analysis. This paper presents an initial investigation if load sequence and weather ... -
Fatigue Assessment of Offshore Wind Turbine Support Structures with the Frequency Domain Method
Sande, Einar Sortland (Master thesis, 2015)Offshore wind energy has shown great potential and can be a great contributor when it comes to solving some of the climate challenges that the world faces today. However, both design and operational cost has been a limiting ... -
Influence of Soil Parameters on the Fatigue Lifetime of Offshore Wind Turbines with Monopile Support Structure
Schafhirt, Sebastian; Page, Ana M.; Eiksund, Gudmund Reidar; Muskulus, Michael (Journal article; Peer reviewed, 2016)Designing support structures for offshore wind turbines is a complex task as these are highly dynamic systems subjected to long-term cyclic loads with variable amplitude. Long-term cyclic loading may cause stiffening or ... -
Lifetime extension for large offshore wind farms: Is it enough to reassess fatigue for selected design positions?
Bouty, Corantin; Schafhirt, Sebastian; Ziegler, Lisa Sabine; Muskulus, Michael (Journal article; Peer reviewed, 2017)Fatigue reassessment within the decision process of lifetime extension might be uneconomical when individually performed for each turbine of a large offshore wind farm. This paper analyses the possibilities to extrapolate ... -
Markov approach to estimate fatigue damage for monopile-based offshore wind turbines
Choy, Cristina Capdevila; Schafhirt, Sebastian; Muskulus, Michael (Chapter, 2018)The Markov approach to estimate fatigue damage for a monopile-based offshore wind turbine exposed to aerodynamic and hydrodynamic loading is investigated in this study. The focus of this study is on obtaining the ... -
Mesh parametric study for fatigue assessment of tubular K-joints using numerical methods
Mendoza Espinosa, Jorge; Schafhirt, Sebastian; Muskulus, Michael (Journal article; Peer reviewed, 2017)Wind turbine jacket structures are complex structures, whose joints design is generally driven by fatigue. These joints, along with their complex welds, are of special interest in terms of cost reduction. Therefore, a ... -
On Fatigue Damage Assessment for Offshore Support Structures with Tubular Joints
Hammerstad, Benedicte H.; Schafhirt, Sebastian; Muskulus, Michael (Journal article; Peer reviewed, 2016)The hot spot stress approach is commonly used for fatigue lifetime estimation of tubular joints. The standard approach consists of the linear superposition of stress components from axial, in-plane, and out of plane action, ... -
On gradient-based optimization of jacket structures for offshore wind turbines
Oest, Jacob; Sandal, Kasper; Schafhirt, Sebastian; Stieng, Lars Einar; Muskulus, Michael (Journal article; Peer reviewed, 2018)During the bidding or very early design phases of jacket structures for offshore wind turbines, there may be very limited information available on meteorological conditions, soil conditions, turbine specifications, etc. ... -
Relative assessment of fatigue loads for offshore wind turbine support structures
Stieng, Lars Einar; Hetland, Ruth; Schafhirt, Sebastian; Muskulus, Michael (Journal article; Peer reviewed, 2015)Time domain analyses of Offshore Wind Turbines involve a lot of computational effort. In this paper, we present a method for reducing this effort by using results from analyses with shorter simulation lengths to predict ... -
Robustness of support structures for offshore wind turbines - Dynamics, fatigue damage and extreme loads with a damaged foundation
Hryniewicki, Konrad Robert (Master thesis, 2015)Abstract This master thesis considers the strength analysis of the offshore wind turbine s jacket support structure with one structural member damaged or weakened, not capable of transferring the loads. A wind turbine and ... -
Sensitivities in fatigue analysis of offshore wind turbine support structures
Hammerstad, Benedicte Hexeberg (Master thesis, 2016)A fatigue analysis gives an answer to the question of whether a structure will resist fatigue throughout its lifetime or not. The hot spot stress approach is one of the methods used to find the solution, by looking at ... -
Sensitivity of wave fatigue loads on offshore wind turbines under varying site conditions
Ziegler, Lisa; Voormeeren, Sven; Schafhirt, Sebastian; Muskulus, Michael (Journal article; Peer reviewed, 2015)Considerable variations in environmental site conditions can exist within large offshore wind farms leading to divergent fatigue loads on support structures. An efficient frequency-domain method to calculate wave-induced ...