Single-blade installation is a popular method for installing blades on bottom-fixed o↵shore wind turbines. A jack-up crane vessel is often employed, and individual blades with their roots equipped with mechanical joints and bolted connections are lifted to the tower-top height and mated with a pre-assembled hub. The final mating phase is challenging and faces significant risks of impact. Due to relative motions between the blade and the hub, substantial impact forces may arise and lead to severe structural damages at root connections, thereby causing delays in the installation task. The present paper considers a realistic scenario of the mating process and investigates the consequences of such impact loads. Here, a single-blade model with tugger lines and a monopile model were established using a multi-body formulation, and relative velocities under collinear wave and wind conditions were obtained. A three-dimensional finite element model was developed for the blade root with T-bolt connections, and an impact investigation was performed for the case in which a guiding connection impacts the hub. The results show severe bending and plastic deformation of the guide pin bolt together with failure of the adjoining composite laminate at the root connection.Based on the type of damage obtained for the di↵erent environmental conditions considered, this paper also discusses its consequence on the installation tasks and suggests onboard decision making in case of an impact incident. The results of this study provide new insights regarding the mating phase and can be utilised to establish response-based operational limits.

For installing offshore wind turbines into deep waters, use of floating crane vessels is essential. One of the major challenges is their sensitivity to wave-induced vessel and crane tip motions, which can cause the impact of lifted components like blades and nacelle with nearby structures. The impact loads on fibre composite wind turbine blades are critical as several complex damage modes, capable of affecting the structural integrity, are developed. Planning of such installation tasks therefore requires response-based operational limits that consider impact loads on the blade along with their damage quantification. The research area considering the impact behaviour of the lifted blade is novel, and thus, the paper identifies vessel, blade and lifting parameters that determine impact/contact scenarios. Furthermore, for a case in which a lifted blade with its leading edge impacts the tower, a numerical modelling technique is presented in Abaqus/Explicit, and a comprehensive damage assessment of the blade and an investigation of the impact dynamics and energy evolution are performed. Sensitivity studies for two distinct blade designs and two different impact locations are considered. The results show that 7-20% of the impact energy is absorbed as damage in the blade, whereas the majority dissipates as rigid-body motions of the blade after the impact. The findings of the study highlight the requirement for advanced installation equipment, such as active tugger lines, to prevent successive impacts of wind turbine blades during installation.

The growing requirements of large sized turbines require heavier components to be lifted to large heights using installation vessels. This imposes an inherent and significant risk of impact to the lifted components especially when floating crane vessels are used. Floating crane vessels are extremely senstive to wave-induced motion causing substantial crane tip responses and can lead to significant damage to the lifted blades. Currently, the planning for such weather sensitive operation does not include explicitly the risk of contact/impact or damage in the components to determine the operational limits. This is important for wind turbine blades owing to the fact that they are made of composite materials and are vulnerable to damage from contact/impact loads. The present paper proposes a novel methodology to determine response based operational limit for the blade installation by considering the structural damage criteria for the lifted blade linked under accidental loads in combination with the global response analysis of the installation system under stochastic wind and wave loads. A case study is presented based on the DTU 10 MW reference blade, lifted horizontally using jack-up crane vessel which impacts the pre-assembled turbine tower with its tip region while being installed under mean wind speed of 10 m/s. It is found that under such conditions, it is safe to install blade from structural damage perspective as the characteristic responses obtained were low to develop any damage and were below the threshold level. The findings of the study can be used to derive limiting sea states for blade installation using floating vessels, however a damage tolerance approach requring residual strength analyisis post impact is compulsory.

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This study investigates the feasibility of utilising common composite material layup techniques in ship propeller blade design to achieve an automatic pitch adjustment through bending-induced twist deformation. A comprehensive design approach, including various reinforcement materials and arrangements, was employed to attain the desired foil pitching, while minimising other undesirable deformation modes. The design process involved iterative computational analysis using finite element analysis and a deformation mode analysis based on foil shape parameters. The research showed that the proposed design approach effectively found options to improve the desired foil parameter pitch, while minimising undesirable deformation modes such as blade deflection and foil shape change. Furthermore, the proposed blade design was tested in thruster steering operational conditions and was found to have a pitch change well matched, potentially countering some changes in fluid flow. When compared to Kumar and Wurm’s design, which only focused on the angular orientation of glass reinforcement, the proposed design was found to outperform the twisting by achieving the same twist for a blade half the length. This study provides valuable insights into the utilisation of composite materials in ship propeller design and highlights the potential for further improvement through a composite engineering design approach.