Turbine Tower Research Articles

Mechanical behavior of prestressed UHPC wind turbine tower columns under combined axial compression and bending

Mechanical behavior of prestressed <scp>UHPC</scp> wind turbine tower columns under combined axial compression and bending

Low-cycle fatigue behaviour of concrete-filled double skin steel tubular (CFDST) members for wind turbine towers

Wind energy has the advantages of being clean and renewable. Wind turbine towers endure horizontal cyclic loads that could influence the performance of entire structure. To clarify the low-cycle fatigue behaviour of concrete-filled double skin steel tubular (CFDST) members, a total of 16 specimens were experimented. The hollow, slenderness, and axial compression ratios are specifically designed to clarify the effects on performance under constant amplitude loading and hysteretic loading conditions. The typical failure modes under both loading conditions and the relationship between loop strain, loop bearing capacity, loop energy dissipation, cycle number, and various degradation indices were analysed. Studies indicate that the failure mode under low-cycle fatigue loading is mainly local deformation, which includes transverse fracture occurring at the region between the steel tube and ribbed stiffener, the crushing concrete. Fatigue specimens with different amplitudes exhibit varying shapes of hysteresis responses. Higher amplitudes could enhance damage and significantly reduce fatigue life. Increasing the hollow and axial compression ratios boosts the energy dissipation capacity, and decreasing the slenderness ratio enhances the lateral resistance. A 2 % constant amplitude preload intensifies the degradation of bearing capacity and energy dissipation under subsequent constant amplitude loading.

Experimental investigations on normal mode nodes as support positions of a resonant testing facility for bending fatigue tests

AbstractLarge‐scale fatigue testing is very important to the research on scale effects, which occur in large cyclic loaded structures, such as wind turbine towers. However, such experimental testing has a very high energy consumption. As an efficient alternative, this paper presents a new resonant testing facility for large‐scale specimens under cyclic bending loads. The facility works as a 4‐point bending test, in which the specimen is supported in the nodes of its first normal bending mode, where theoretically no reaction forces occur. Two counter‐rotating imbalance motors with excitation frequencies near resonance generate a harmonic force acting on the specimen. Experimental trial fatigue tests on a steel pipe as a specimen were carried out, in order to validate the new testing setup. A great decrease in the support forces was reached by placing the supports at the normal mode nodes. Additionally, the behavior of the support forces under varying positions and excitation frequencies was also investigated. In summary, the resonant testing method combined with the supports at the normal mode nodes offers an efficient and energy‐saving testing setup for large‐scale fatigue tests.

Structural Design and Research of Offshore Wind Turbine Towers

The structural design and research of offshore wind turbine tower need to involve knowledge and technology in many fields, such as mechanical engineering, material science, fluid mechanics and so on. Through the research and optimization of tower structure, it can promote the development of related industries and improve the technical level and competitiveness of the whole industrial chain. The structural design and research of offshore wind turbine tower has important practical significance and application value. Through in-depth research and optimization of design, the performance and reliability of offshore wind turbines can be improved, and the rapid development of offshore wind power technology can be promoted.

Study on the Dynamic Characteristics of a Wind Turbine Tower Based on Wind Tunnel Experiments

Study on the Dynamic Characteristics of a Wind Turbine Tower Based on Wind Tunnel Experiments

Crack Detection Method for Wind Turbine Tower Bolts Using Ultrasonic Spiral Phased Array.

High-strength bolts are crucial load-bearing components of wind turbine towers. They are highly susceptible to fatigue cracks over long-term service and require timely detection. However, due to the structural complexity and hidden nature of the cracks in wind turbine tower bolts, the small size of the cracks, and their variable propagation directions, detection signals carrying crack information are often drowned out by dense thread signals. Existing non-destructive testing methods are unable to quickly and accurately characterize small cracks at the thread roots. Therefore, we propose an ultrasonic phased array element arrangement method based on the Fermat spiral array. This method can greatly increase the fill rate of the phased array with small element spacing while reducing the effects of grating and sidelobes, thereby achieving high-energy excitation and accurate imaging with the ultrasonic phased array. This has significant theoretical and engineering application value for ensuring the safe and reliable service of key wind turbine components and for promoting the technological development of the wind power industry.

Controlling wind turbine tower vibration under external force by applying control systems combination

The global focus has recently shifted away from fuel-based power sources, and one of the most important projects for energy production is wind energy. To maintain low costs, the current research examines the problem of vibrations affecting wind turbine towers’ performance (WTTs). In particular, the tower, resulting from excessive vibrations, can negatively affect a structure’s power output and service life, as it can cause fatigue. Therefore, we conducted numerical tests on various types of controlled systems. Our tests revealed that combining a new technique cubic negative velocity control (CNVC) and linear negative acceleration control (LNAC) was the most effective and cost-efficient option for vibration damping. This solution was derived by using an approximation method for the averaging technique. The external force is an important component of a nonlinear dynamic system and can be characterized by two-degree-of-freedom (2-DOF) differential coupled equations. After implementing the control measures, we conducted a numerical analysis of the vibration values before and after the operation. Stability is studied numerically. The numerical and approximate solutions were confirmed through the frequency response equation and time history with fourth-order Runge–Kutta (RK-4). Finally, we investigated the effect of parameters and compared our results with those of previously published studies.

Application of laced built-up columns with cold-formed lipped angle sections in wind turbine towers

Increasing the height of wind turbine towers effectively enhances their power output. Consequently, there is a growing demand for constructing wind turbine towers with higher hubs, especially in heavily populated and energy-intensive areas. Traditional approaches involve enlarging angled steel, posing production challenges and economic feasibility concerns. This study proposes replacing traditional angled steel with cold-formed lipped angles for improved structural performance. In this paper, a finite element model of the built-up column with cold-formed lipped angles is developed through ANSYS software. Finite element calculations are applied to various cross-sectional dimensions of cold-formed lipped angle sections to analyze column curves. Incorporating calculation methods from international standards, the paper presents a fitting formula and calculation method for the load-carrying capacity of the built-up column with cold-formed steel lipped angle sections. Finally, utilizing a wind turbine tower with a 120 m hub height as a case study, the paper conducts structural modeling and design analyses for both the built-up column with cold-formed lipped angles and the one with conventional angled steel. The research indicates that after adopting the built-up column with cold-formed lipped angle sections, the stress ratio of the tower columns is significantly reduced, with an approximate 16 % decrease in the stress ratio of the most critical section. The adoption of cold-formed lipped angle section effectively enhances the overall load-carrying capacity of the wind tower, providing a greater safety margin for the design. The calculation method provides valuable insights for future engineering applications.

Wind Tunnel Test Research on the Aerodynamic Behavior of Concrete-Filled Double-Skin Steel (CFDST) Wind Turbine Towers

To explore the potential application of concrete-filled double-skin steel tubular (CFDST) structures in wind turbine towers, this study carried out wind tunnel tests to explore the aerodynamic behavior of CFDST tower-based wind turbine systems. Two scaled models including traditional steel tower-based and CFDST tower-based wind turbine systems were designed and tested in the field of typhoons. Then, the vibration characteristics in both the downwind and crosswind directions were systematically investigated, in terms of acceleration and displacement response, motion trajectory, dynamic characteristics, etc. The findings demonstrate that CFDST structures can have significantly improved performance against both blade harmonic excitation and external environmental excitation. Compared to traditional steel towers, CFDST towers exhibit a substantial reduction in aerodynamic response. In particular, the reduction in the RMS value can be over five times in the resonance case and 457.69% in the non-resonance case. The CFDST towers predominantly exhibited converged motion trajectory and concentrated on lower vibration modes. The energy dissipation capability was remarkably enhanced, with the damping ratio increasing up to 40.98%. Overall, it was experimentally demonstrated that CFDST towers can efficiently address the dynamic problems of large-scale wind turbine towers in engineering.

A closed-form expression derived from virtual testing for structural optimization of L-flange bolted connections

L-flange bolted joints are extensively used in different industrial sectors, such as wind turbine towers, rocket stages, or pipelines. Typically, the design of these connections is based on analytical expressions derived from simplified beam models. However, the influence of specific factors such as curvature, adjacent bolts, or joint separation are not addressed within conventional approaches. Finite element models offer the advantage of comprehensively accounting for these effects and the interaction between different failure mechanisms. Nevertheless, their industrial implementation requires significant computational resources, in contrast to the use of analytical formulae. In this context, this paper proposes a new framework for designing optimized L-flange bolted connections, based on general closed-form expressions that rely on validated numerical results. Three expressions, each one related to a particular failure mechanism, are derived from parametric simulations varying the most influencing parameters in the structural behavior. The generated equations can be easily implemented to guide the design process towards an optimal configuration, taking advantage of beneficial effects not addressed within classical approaches. A closer prediction of the actual load capacity of the joint can be obtained, providing a tool that allows engineers to make more reliable and economical designs.

Nonlinear analysis of a wind turbine tower with a tuned liquid column damper (TLCD)

Nonlinear analysis of a wind turbine tower with a tuned liquid column damper (TLCD)

Ice-Induced Vibration Analysis of Fixed-Bottom Wind Turbine Towers

This research tackles the challenge of ice-induced vibrations in fixed-bottom offshore wind turbines, particularly the risk of frequency lock-in (FLI), a critical loading condition arising from slow ice movement against structures. We introduce an innovative FLI analysis process grounded in the ductile damage–collapse (DDC) mechanism, which offers a more accurate and significantly lower probability of FLI occurrence than conventional methods. Through dynamic evaluations employing a time-domain ice load model and FLI displacement analyses, we demonstrate that FLI can lead to higher structural vibrations than those caused by continuous brittle ice crushing. A case study of a 5 MW monopile wind turbine tower utilising Abaqus confirms the necessity for incorporating FLI considerations into structural design to ensure safety and performance in ice-prone environments. Comparing the DDC mechanism with the ISO method, our study reveals that the DDC approach predicts higher displacement and acceleration values during FLI, nearly an order of magnitude greater than those induced by ice loads with a 50-year return period. The research underscores the importance of robust ice-load integration in design strategies for offshore wind turbines, especially in regions susceptible to ice. It highlights the DDC mechanism as a novel strategy for enhancing structural resilience against ice-induced hazards.

Comparison of Alternatives for Multi-MW Wind Turbine Towers in Northern Patagonia, Argentina

Comparison of Alternatives for Multi-MW Wind Turbine Towers in Northern Patagonia, Argentina

Potential and Limitations of Anomaly Detection via Tower-Radar Monitoring of Wind Turbine Blades in Regular Operation with Convolutional Networks

The authors have already presented a first analysis of a field study on radar- based structural health monitoring of rotor blades on two operational wind turbines. This analysis will now be extended with measurements from a third operational wind turbine used as a case study for structural monitoring of individual rotor blades over different time intervals and blade modifications. More precisely, a sensor box with a 35 GHz FMCW radar and a highspeed camera was positioned at 90m height on the turbine tower, collecting radar data for structural information and videos for automatic ground truth labelling. After two months of collecting data, each individual rotor blade of that turbine was differently modified and measured again. The radar-facing surface of one rotor blade was partially coated with a microwave absorber foil, while an equivalent foil was applied to the backside of the second rotor blade. The third rotor blade was intentionally left unchanged for the sake of comparability. This study investigates potential limitations like general dataset complexity in radar-based anomaly detection for operational wind turbines. Furthermore, the discriminative ability of a convolutional neural network for classifying moving rotor blades is discussed when encountering feature drift through changing environmental and operational conditions, i.e. metadata like nacelle orientation, rotor blade pitch and rotation speed.

Effects of carbon nanotubes and carbon fibers on the properties of ultra-high performance concrete for offshore wind power generation

Ultra-high performance concrete (UHPC), as one of the most eye-catching building materials, has been the subject of extensive research by scholars. On this basis, to expand the application of UHPC for offshore wind turbine towers in complex marine environments, three different fiber materials - copper-plated microfibre steel fibers, carbon fibers, and carbon nanotubes (CNTs) - have been selected for the study of the possibilities of further improving the mechanical properties of UHPC. This study focused on understanding the impact of various fiber combinations and dosages on the flowability, compressive strength, flexural strength, and tensile strength of UHPC. Our findings indicate that carbon fiber, when present at a concentration of up to 0.5%, the effect on the fluidity of UHPC is only about 1.05%. However, the addition of CNTs significantly diminishes the flowability of UHPC, with a consistent decrease observed as the CNT content increases. Notably, when carbon fiber and CNTs are used in combination, the maximum reduction in flowability reaches 7.8%. Furthermore, as the dosage of these fibers increases, the compressive strength, flexural strength, and tensile strength of UHPC all demonstrate a positive trend of improvement. It is observed that the optimal performance is achieved when both carbon fiber and CNTs are present. In particular, carbon fiber exhibits a more profound impact on enhancing compressive strength and flexural strength, when carbon fibers were doped by volume at 0.5%, the compressive and flexural strengths were increased by 6.7% and 11.7%, respectively, compared to the control group, while carbon nanotubes increased the tensile strength by 7.4% at lower dosage. These findings highlight the potential of fiber combinations to optimize UHPC’s mechanical properties for various engineering applications..

Integration of Wind Power for Sustainable Energy at Lagos State University of Science and Technology: A Feasibility Study

This study investigates the feasibility of integrating wind power generation at Lagos State University of Science and Technology, specifically within the Mechanical Engineering Department, to address persistent electricity supply challenges in Nigeria. The research focuses on the application of a five-bladed horizontal axis wind turbine (HAWT) and emphasizes the urgent need for sustainable energy solutions due to the depletion of conventional sources and the environmental impact of fossil-fuel-powered generators. The methodology involves mathematical modelling to analyze wind shear exponent, Weibull distribution, maximum power available, and capacity factor. Utilizing the FZ-3000 five-bladed HAWT, data is collected using a wireless wind anemometer. The results reveal a calculated wind shear exponent aligned with terrain characteristics, emphasizing the impact of obstructions on wind speed. Analysis of average wind speed throughout the day demonstrates the potential for continuous power generation at the Mechanical Engineering Department of the Lagos State University of Science and Technology. Examination of wind speed at different heights underscores the significance of elevated turbine towers for capturing higher wind speeds and optimizing power output in the specific context of Lagos State University of Science and Technology. The calculated capacity factor of 44.17% suggests the viability of large wind turbine installations within the Mechanical Engineering Department, with room for improvement through routine maintenance. This research contributes valuable insights into harnessing wind power at Lagos State University of Science and Technology, particularly within the Mechanical Engineering Department, addressing technical and environmental challenges for sustainable energy development.

Multi-objective parameter optimization of large-scale offshore wind Turbine's tower based on data-driven model with deep learning and machine learning methods

The tower plays a crucial role in wind turbine systems. However, the design and optimization of configuration parameters have traditionally been lacking in intelligent methods. This study proposes a multi-objective parameter optimization framework that incorporates artificial intelligence models. Specifically, the diameters and thicknesses of the tower are the design parameters that strongly influence two conflicting optimization objectives: mass and top deflection. The nonlinear relationship between these parameters is predicted using surrogate models, such as the Convolutional Neural Network (CNN), Back-propagation Neural Network (BPNN), and Support Vector Machine (SVM), which serve as optimization functions. Additionally, the solutions must meet the requirements for frequency, stress, and buckling. In this study, two reference wind turbines, namely, IEA-15-240 and IEA-22-280, are selected as case studies, and the open-source software WISDEM is utilized to construct the training and testing datasets. Bayesian optimization is used to fine-tune the hyperparameters. Results show that the CNN model outperforms others with larger datasets. Leveraging Deep Learning in the design of offshore wind turbines can significantly reduce mass and deflection while maintaining integrity and performance.

Wind-Induced Response Analysis and Fatigue Reliability Study of a Steel–Concrete Composite Wind Turbine Tower

Taking an actual 3MW steel–concrete composite wind turbine tower as an example, a finite element model of the tower structure was established, and static bearing capacity and dynamic time history response analyses were performed to identify the locations where the structure is prone to failure. On this basis, the fatigue lives of the turbine tower at the most unfavorable locations were predicted using linear cumulative damage theory, and the fatigue reliability at the corresponding locations of the structure was calculated using the kriging–subset simulation method. The most dangerous locations of the tower that are most prone to failure are as follows: the bottom of the leeward side of the upper steel tube, the flange of the steel tube, the bolt-hole imprinting surface of the flange, the leeward side of the transition tube, and the top of the leeward side of the concrete tube. The failure risk of the flange and bolt-hole imprinting surface of the upper steel tube is relatively high, followed by that of the transition tube. This indicates that special attention should be given to the design and daily maintenance of this part. The fatigue resistance of the tower can be enhanced by improving the strength of the flange plate or increasing the number of bolts and strengthening the transition tube.

Two-Scale Probabilistic Seismic Fragility Assessment for a Prestressed Concrete-Steel Hybrid Wind Turbine Tower with Incremental Dynamic and Multiple Stripe Analysis

ABSTRACT To evaluate the seismic performance of a prestressed concrete-steel hybrid (PCSH) wind turbine tower, the seismic fragility curves based on incremental dynamic analysis (IDA) and multiple stripe analysis (MSA) on a two-scale model are presented and compared. The peak ground acceleration (PGA) and peak lateral drift on the top of the tower are adopted as the intensity measure (IM) and engineering demand parameter (EDP) of analysis, respectively. Finally, the seismic performance of the PCSH tower subjected to seismic action at different soil is investigated. The fragility curves obtained by IDA and MSA methods are compared.

Experimental investigation on vibration suppression of a new prestressed TMD for wind turbine towers

The pendulum tuned mass damper (PTMD) has been popular for vibration suppression due to its particular configuration form and frequency-tuning pattern. Based on the theoretical and numerical methods, a new prestressed TMD (PSTMD) has recently been presented which has better performances than the PTMD. To verify the improvement advantage and applicability comparatively, a comprehensive experimental study is carried out to investigate the vibration suppression of PSTMD in this paper. A wind turbine tower (WTT) with the lump-mass of the PSTMD can be represented by a two-degrees-of-freedom system, and its optimal design parameters can be analytically derived. Three test specimens, including the uncontrolled WTT, and the WTT with the PTMD or the PSTMD were tested in the laboratory with different equivalent wind and seismic loads via a shaking table. The presence of the PTMD or the PSTMD is noted changing only slightly the natural frequency and mode shape of the WTT, and the PSTMD exhibits the superior vibration suppression capability compared with the traditional PTMD.