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Item type:Publication, Access status: without files , Integration of oscillating water column wave energy converter into an aquaculture system: Numerical investigation of hydrodynamic interactionsThe expansion of offshore aquaculture into deep-water areas is hindered by energy supply limitations, as conventional diesel-powered systems suffer from high fuel transport costs, and greenhouse gas emissions. Wave energy offers a promising alternative; however, existing W ave E nergy C onverters (WECs) have high capital costs and limited suitability for harsh offshore environments, particularly when integrated with aquaculture platforms via mechanical connectors, flexible cages, or mooring-based coupling. This study presents the evaluation of the hydrodynamic behavior of the first direct integration of an O scillating W ater C olumn (OWC) WEC with a steel semi-submersible aquaculture cage to form a single unified body without any intermediate connectors. A RANS–VOF numerical framework was developed, incorporating an advanced forcing zone method and discretized by the finite volume method, to simulate the dynamic response of the hybrid system under regular waves. The influence of the OWC bottom configuration was quantified by varying the bottom inclination angle, representing the investigation of bottom-slope effects on a floating OWC–WEC integrated with an offshore aquaculture cage. The results indicate that adapting the OWC–WEC design parameters enhances power output and damps platform motion, thereby improving offshore survivability. Furthermore, the optimized design increases energy conversion efficiency, supports economic feasibility, and provides a robust foundation for the development of integrated offshore aquaculture–wave energy systems.Publicationtype: Journal Article18 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Simulated ice loads on a ship propeller and comparison with full-scale measurements(Elsevier, 2025-10-15); ; ; ; A methodology to better estimate the loads of ice acting on the propeller of a ship is developed. Based on measurements conducted in the North Pole region, an existing failure model for ice based on the Mohr–Coulomb nodal split approach is modified to better represent the lower strength of polar ice compared to laboratory ice. The modified material model for the sea ice is used to compute the propeller torque and a load spectrum for the propeller-ice interaction of the research ship S.A. Agulhas II. To this end, a floe-ice breaking simulation is used to estimate the size and shape of the ice cusps hitting the propeller of this ship. In the next step, a set of finite element simulations of the propeller-ice interaction utilizing the modified Mohr–Coulomb nodal split model is conducted. Based on this, the load spectrum is computed and compared with the measured torque on the propeller shaft of the S.A. Agulhas II. The successful reproduction shows the applicability of the approach to better estimate the loads exerted by the ice on the propeller.Publicationtype: Journal Article55 31 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Ultra-low cycle fatigue of ship hull structure: an alternately-cyclically loaded four-point bending test of a large box girder(Elsevier, 2025-03-15); ; ; Ultra-low cycle fatigue (ULCF) refers to material failure at small number of loading cycles. For large complex structures like ships, the damage from ULCF can bring hazardous consequences. In this study, an alternately-cyclically loaded four-point bending test of a large box girder is introduced as the specimen to represent the ULCF of ship hull structure. In every load during the test, large deformation is applied to the specimen even after reaching its ultimate hull girder strength (UHGS), thus extensive plastic deformation and obvious fracture can occur in the specimen. The severely damaged specimen is further tested until 1.5 cycles of bending are finished, thus the test of post-damage box girder is realized. Moreover, the box girder is divided into 3 sub-sections, which show different but still interacting structural behavior. The result of the test shows the structural behavior of a large complex structure suffering severe damage during alternate hogging and sagging after reaching its UHGS, which corresponds to the consequence of ULCF. The presented ULCF test also provides experiences for investigations of large complex structures with existing damages or after accidental loads. Considering the number of cycles in the test, this study can bridge the gap between monotonic overload and ultra-low cycle fatigue.Publicationtype: Journal Article27 44 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Experimental and numerical investigations of the ultimate strength of two subsea power-transmission cablesIntegration of renewable energies into existing grids must be safe and reliable including the subsea power-transmission cables. Therefore, this paper determines the purely mechanical ultimate strength of a DC and an AC power transmission cable under axial load. Aspects concerning the electrical functionality of these cables are outside the scope of this paper and failure of the cable is defined as rupture of the cable following ultimate strength. At first, the individual components of the cable are tested to obtain the engineering stress strain relationships to derive material model data for the numerical simulation of the components and cables. The latter is compared to full-scale experimental results of the power transmission cables. Very good comparison of the numerical and experimental ultimate strength of the cables was achieved with the presented straightforward procedure.Publicationtype: Journal Article43 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Review of methods for the high-cycle fatigue strength assessment of steel structures subjected to sub-zero temperature(2022-03-01); In recent years, there has been a growing interest in exploring the resources of the Arctic regions and an increase in shipping in regions with seasonal sub-zero temperatures. Such low temperatures impose challenging requirements for the structural integrity of steel structures and their weldments. Hence, specific knowledge of the behavior of materials and weldments and how to account for temperature effects is crucial to ensure safe operations. A number of recent studies have shown that fatigue strength at sub-zero temperatures is a major knowledge gap. This is exacerbated by the fact that this effect is not addressed in international standards. In this context, this study presents a comprehensive review of the current state of the art of high-cycle fatigue strength assessment methods for steel structures subjected to sub-zero temperature. The main objective is to provide an overview of how to account for temperature effects on fatigue strength when designing steel structures.Publicationtype: Journal Article58 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Fluid-structure interaction and stress analysis of a floating wind turbineIn this paper, we describe a method to investigate the fluid-structure interaction of a floating wind turbine and to analyze the global deformations and the corresponding stresses with a detailed finite element model. To solve the fluid-structure interaction problem, a partitioned approach is chosen. The in-house C++ library comana, which was developed to solve multi-physic problems by coupling existing solvers, is extended to couple the fluid solver panMARE and the structural solver ANSYS. The significance of the interaction of structural deformations and the fluid loads is pointed out for the rotor of the wind turbine. In order to enable the use of a detailed finite element model in the fluid-structure interaction simulation, a model reduction method is applied in ANSYS. As a result, an efficient stress analysis can be performed under consideration of the fluid-structure interaction.Publicationtype: Journal Article114 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , The ISSC 2022 committee III.1-Ultimate strength benchmark study on the ultimate limit state analysis of a stiffened plate structure subjected to uniaxial compressive loads(Elsevier, 2021-06-03); ; ; ; This paper presents a benchmark study on the ultimate limit state analysis of a stiffened plate structure subjected to uniaxial compressive loads, initiated and coordinated by the ISSC 2022 technical committee III.1-Ultimate Strength. The overall objective of the benchmark is to establish predictions of the buckling collapse and ultimate strength of stiffened plate structures subjected to compressive loads. Participants were asked to perform ultimate strength predictions for a full-scale reference experiment on a stiffened steel plate structure utilizing any combination of class rules, guidelines, numerical approaches and simulation procedures as they saw fit. The benchmark study was carried out blind and divided into three phases. In the first phase, only descriptions of the experimental setup, the geometry of the reference structure, and the nominal material specifications were distributed. In the second phase, the actual properties of the reference structure were included. In the third and final phase, all available information on the reference structure and measured properties were distributed, including the material properties and laser-scanned geometry. This paper presents the results obtained from seventeen submitted FE simulations as well as details on the experiment. It also presents comparisons of the force versus the displacement curve, failure modes and locations for each phase, among others, and a discussion on the participants’ ability to predict the characteristics of the reference experiment with the information that is available for the phase. The outcome of the study is a discussion and recommendations regarding the design of finite element models for the ultimate state analysis of stiffened plate structures, with emphasis on the prediction of the ultimate capacity, force-displacement curve, and failure mode and location related to access to data, uncertainties and modeling of the material properties, geometric imperfections and distortions, and residual stresses.Publicationtype: Journal ArticleScopus© Citations 27 96 208 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , The measurement accuracy of instrumented ship structures under local ice loads using strain gaugesStrain gauges are commonly used for the instrumentation of ship structures to measure ice loads on the basis of shear strain differences. Finite Element Analysis (FEA) is used to determine the load–strain relation of the instrumented area by calculating an Influence Coefficient Matrix (ICM). However, the accuracy of the measurement method and the influence of the load location and load length on the accuracy of the load determination are rarely assessed. Consequently, this paper identifies the accuracy of the ICM, discusses which structures are suitable for measurements of shear strain differences and presents possible improvements regarding these measurements. As load cases are systematically varied over a finite element model, the external load is recalculated based on the resulting shear strains. The number of strain gauges used for the measurement of shear strains has a significant impact on the ICM. For common instrumentation it was found that the ice load can only be accurately determined, if the ice load acts within the instrumented area. To overcome this limitation, an approach to determine the load location is presented among further recommendations.Publicationtype: Journal Article104 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Pragmatic regularization of element-dependent effects in finite element simulations of ductile tensile failure initiation using fine meshes(2020-11); For the evaluation of the structural response in accidental scenarios like ship collisions, the simulation of tensile failure initiation is inevitable. Here, one difficulty is that the process of failure initiation is a very local process, which cannot be simulated in its details at present due to the computing effort which would be required. However, there are various approaches how the failure initiation can be simplified and simulated in finite element models of large thin-walled structures. A short overview of these approaches is given. A pragmatic approach, which is suitable for relatively small elements for the simulation of failure initiation in uniaxial to biaxial stress states, is chosen within this paper for further investigations regarding the applicability for thin-walled steel structures. Exemplary simulations with solid and, in particular, shell elements are used to demonstrate how the effects of element size and other element properties can be considered in the simulation of failure initiation. The focus is also on imperfections that are relevant in simulations with small elements. For this purpose, an indentation experiment is simulated with different imperfections.Publicationtype: Journal Article94 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Inverse modeling approach for transformation of propeller shaft angular deformation and velocity to propeller torque load(2019-09); ; In full-scale trials or model-scale tests, the propeller torque load is typically measured indirectly on the propeller shaft. Due to structural flexibility and mass of the propeller and propeller shaft, the measured propeller shaft torque response includes a time delay and amplitude difference compare to the propeller load. These differences are usually small during propeller operation, but may be significant during transient states (i. e. starting of the engine, rough sea, or operation in ice-covered waters). In this paper, an inverse model is used to calculate propeller load based on the propeller shaft response. The results indicate that the inverse model can be less complex than the complete propulsion machinery model and consider only the propeller and propeller shaft. Several modeling approaches are tested based on four proposed measuring setups and three forms of system discretization. Out of five inverse modeling approaches, two approaches showed the ability to transform measured propeller shaft angular deformation and velocity responses, colored with noise, into the corresponding rule-based propeller torque load with acceptable accuracy. Furthermore, the robustness of the inverse approaches to the random ice-propeller interaction, sampling frequency, measuring location along the propeller shaft and starting time (before and during ice-propeller interaction), is discussed.Publicationtype: Journal Article163