Wind Loads Research Articles

Investigation of the wind loads and flow patterns of a high-rise building under twisted wind flows based on LES

The twisted wind effect has attracted increasing attention among scholars due to its significant influence on the wind loads and wind induced responses of high-rise buildings. Nowadays, it is still challenging to simulate twisted wind flows (TWFs) with larger wind twist angles (WTAs) in the wind tunnel test. Compared to wind tunnel test limitations, the large eddy simulation (LES) offers an effective tool to simulate a broader WTA range. Several state-of-the-art numerical studies have generated TWFs that rely on multiple velocity inflow boundary (MVIB), but it results in vast computational domains and substantial abnormal pressure fluctuations. This paper proposes a single velocity inflow boundary (SVIB) method for modeling TWFs, which can significantly reduce the computational domain size without losing accuracy. Based on the SVIB method, we simulate TWFs with four WTAs (i.e., 0°, 25°, 35°, 45°) and conduct a comprehensive analysis of the influence of WTA and wind direction angle on both the wind load characteristics of and the flow patterns around a high-rise building. The results show that the TWFs will twist the vortex topology and trajectory, and the maximum extreme local resultant force coefficient under 35TWF is larger than that under SWF by around 10 %. The positive and negative wind pressures can simultaneously occur on a special surface at large WTAs (e.g., 35°, 45°), which may impose significant shear forces on the intermediate layers. The wind veering effect enhances the contribution of vortex shedding to the longitudinal fluctuating wind loads and the influence of incoming turbulence on lateral fluctuating wind loads. This study contributes to providing a more effective LES method to simulate TWFs with large WTAs and to reveal the effect of large WTA on the wind load characteristics of high-rise buildings under TWFs and the underlying flow mechanism, which is beneficial to the future wind-resistant design of skyscrapers.

Short term hydropower scheduling considering cumulative forecasting deviation of wind and photovoltaic power

The cumulative forecasting errors of wind and photovoltaic (PV) power pose serious challenges to the short-term scheduling of hydropower stations that connected to the same regional power grid. The variable and intermittent nature of wind and PV power necessitate a flexible power source to achieve power balance. Consequently, hydropower, with its flexible adjustment capability, plays a crucial role in supporting the consumption of wind and PV power stations in short-term scheduling. Meanwhile, to address the grid's peak shaving requirement, the scheduling of cascaded hydropower system becomes increasingly complex. Given the limitations of current wind and PV power output prediction technologies, achieving precise forecast remains challenging. In practice, the actual outputs of wind and PV power stations often diverge considerably from predicted values over multiple consecutive periods. This variability may result in the underutilization of wind and PV power if the reserve capacity of hydropower stations is insufficient. Therefore, it is essential to account for the cumulative deviation in electricity from wind and PV sources. By computing probability distribution and establishing boundary condition of the cumulative deviation, the operation of the cascaded hydropower system can be controlled more effectively, thus enhancing the stability of a multi-energy complementary system. This study employs Gaussian Mixture Model (GMM) to characterize the probability distributions of cumulative electricity deviation across multiple periods of wind and PV power and takes it as restriction to regulate the operation of hydropower stations. In order to balance the deviation electricity, the downward electricity reserve, upward electricity reserve and the storage energy of the cascaded reservoirs are introduced as restrictive conditions. The proposed Hydro-wind-PV peak shaving model is then applied to the short-term optimal scheduling of the Lancang River cascaded hydropower system to validate the feasibility and efficacy.

Investigation of wind loads on angle steel columns in lattice structures via force measurement method on members

As the demand for precise prediction of fatigue and collapse continues to grow, it is imperative to conduct research on wind load calculation methods for lattice structures using members as the fundamental unit. This study focuses on the tower body of an angle steel lattice structure with a rectangular cross-section. The aerodynamic characteristics of entire segments, column members in lattice structures, and a single angle steel were investigated, along with the aerodynamic interference effects on members within lattice structures. The research findings indicate that drag coefficients cannot universally substitute the SRSS coefficients of column members or a single angle steel across all wind directions. Therefore, considering that the drag coefficient of the column member or single angle steel surpasses 98% of their SRSS coefficients at a wind direction of 45°, a particular skewed wind load factor was defined, and its fitting formula was proposed. Additionally, a calculation method for wind loads on columns within lattice structures was developed, introducing the concepts of SRSS angle and aerodynamic interference factors on members. The comparison among the experimental data, fitting formula, and proposed calculation method, were conducted. To facilitate the practical application, the simplified formulas for both AIF and SRSS were recommended.

Correlation analysis and joint probability density function model of wind pressures: Focusing on multivariate wind loads field on low-rise building under typhoon climate

The characteristics of the multivariate wind loads field on the roof are crucial to the wind-resistant design of low-rise buildings, which contain the correlation characteristics in space and probability characteristics in the time domain. This paper proposes a framework for constructing a Joint Probability Density Function (Joint PDF) model for a multivariate wind loads field. It provides a detailed correlation analysis for the first time. This paper employs wind pressure data collected from the roof of a low-rise building during Typhoon Muifa. It was found that the correlation becomes more robust with increasing roof pitch and the wind pressures are strongly correlated with a correlation coefficient exceeding 0.50 when the roof pitch is above 15°. The mixture distribution model is applied to the probability density function fitting procedure of wind pressure time series under typhoon climate, and the fitting effect is significantly better than other classical probability density functions. The optimal copula function is determined according to the Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC) for estimating the Joint PDF. The results reveal that Gumbel-copula and Student-copula have the highest proportion in optimal copula functions, accounting for over 90% of the total copula functions. Then, a bivariate Joint PDF for wind pressures are established with the optimal copula function. Additionally, the comparison between measured bivariate Joint PDF and that constructed using copula functions verifies the accuracy of the proposed framework for constructing Joint PDFs. The Joint PDF of wind pressures can enhance the understanding of the stochastic characteristics of local wind load fields on roofs, and the correlation characteristics in space provide crucial references for improving the accuracy of wind load random field simulation and saving the cost of wind resistance design.

Investigation of mooring breakage impact on dynamic responses of a 15 MW floating offshore wind turbine

The stability and integrity of the mooring system are some of critical factors affecting the safety and performance of floating offshore wind turbines (FOWTs). For this reason, it is necessary to investigate the dynamic responses of the rotor, platform, and the remaining cables of the FOWT subjected to mooring breakages. This is because a mooring breakage significantly increases the risk of damage to the FOWT, especially for a nonredundant mooring system. This study has analyzed the platform motions and mooring tension of a 15 MW FOWT, where each offset column connects to two and three mooring lines to enhance the redundancy of the mooring system. The fully coupled simulations of the FOWTs under mooring breakage scenarios are examined using the well-validated numerical framework, OpenF2A, to consider wind, wave and current loading combinations. The result reveals that the breakage of a single mooring has a minor impact on the aerodynamic performance and aeroelastic response of the FOWT for both mooring system configurations. Notably, the platform experiences significant surge and sway when the upwind mooring breaks, leading to a sharp increase in tension of the remaining mooring lines positioned in the same direction. Moreover, the occurrence of snap load events is another factor resulting in the abrupt increase in the mooring tension. However, the maximum tension in the remaining mooring lines has not exceeded the threshold of breaking stress for both redundant mooring systems. The mooring configuration with two catenary cables connected to each column is suggested for the station-keeping system of the 15 MW FOWT considering the dynamic behavior and manufacture cost.

Wind loading on gable and multi-span roof buildings: Comparison between field monitoring, wind tunnel experiments, and design code provisions

The wind loading provisions in the National Building Code of Canada (NBCC) have not been updated for decades despite developments in wind tunnel methods since the original source data. This study aims to review the Nbcc 2020 provisions compared to wind tunnel experiments, field measurements, and the ASCE 7–22 provisions for single and multi-span gable roof buildings. Field measurements and wind tunnel tests are used to collect data for an isolated building and later for a multi-span gable. The pressure coefficients from the field measurements were mostly higher than the wind tunnel, which is consistent with previous studies. The results provided evidence that NBCC provisions for single-gabled roofs (with slope 7∘<α≤27∘) and multi-span gabled roofs (with slope 10∘<α≤30∘) are currently underestimated. New provisions are suggested for the corner (c), edge (s), and field (r) zones of the single-span gabled roof and for gable-end-edge (s’) zone of the multi-span. It is suggested to merge Zone s into Zone c to form a new perimeter Zone p for the single gabled roof and to merge Zone s’ into Zone c for the multi-span gabled roof. The proposed changes correct the current provision underestimation and add simplicity for easier construction.

Revisiting Maximum Log-Likelihood Parameter Estimation for Two-Parameter Weibull Distributions: Theory and Applications

In this article, we reexamine properties of maximum log-likelihood parameter estimation for two-parameter Weibull distributions which have been applied in many different sciences. Finding reasons for this popularity is a key question. Our main contribution is a thorough existence and uniqueness proof for a global maximizer with respect to the parameter space. We first provide existence and uniqueness of local maximizers by Schauder’s first fixed point theorem, monotony arguments and local concavity of its Hessian matrix. Thus, we can prove our main result of existence and uniqueness of a global maximizer by considering all limiting cases with respect to the parameter space. We finally strengthen our theoretical findings on four data sets. On the one hand, two synthetic data sets underline our need for our data assumptions while, on the other hand, we choose two data sets from wind engineering and reliability engineering to demonstrate usefulness in real-world applications.

A novel energy harvesting technology from the movements of air masses

The displacement of air masses caused by the movement of objects or vehicles is often characterized by considerable energy content, which, with appropriate technologies, can be partially recovered. In this sense, numerous scientific works consider rail transport as a possible context for application. However, the literature in the sector highlights how using existing wind technologies in these areas involves many difficulties, mainly related to the turbulent and impulsive nature of the airflows generated. This work presents the architecture and general aspects of an innovative technology for obtaining electrical energy from variable and impulsive airflows, such as those due to the rapid transit of railway trains in tunnels, without precluding its use in other similar fields. The innovative aspect mainly concerns the independent control of two distinct typologies of bladed elements, which can also have translational movement and drag-based and lift-based aerodynamic behavior to improve the adaptability of the embodiment to the site’s fluid dynamic and geometric characteristics. Furthermore, the structural simplification of the apparatus, shifting some of the technological complexity to the control systems, brings further advantages in terms of construction cost, robustness, maintenance, reuse, and transferability to different contexts. Of course, the counterpart of these benefits lies in the software and hardware of the control devices. Analytical models to determine the non-dimensional performance coefficients of the two basic types have been reported as has the architectural model of the control system. The technology shown in this work is protected by an EP and US Patent.

Numerical Analysis of Spoilers and Chamfered Corners for Mitigating Wind Loads on Low-Rise Flat Roof Buildings

Numerical Analysis of Spoilers and Chamfered Corners for Mitigating Wind Loads on Low-Rise Flat Roof Buildings

Experimental study of the out-of-plane mechanical properties of tall foam ceramic (FC) partition wall

Foamed ceramic (FC) partition wall is a non-structural component which has a broad application prospect. At present, most of the relevant specifications and studies on partition walls are limited to ordinary floor heights. In practical engineering applications, the partition wall exceeding the specification height limit often appears in scenes such as hotel halls and airport terminal. It would pose a life safety threat to the building in the event of out-of-plane damage of this type of partition wall under wind loads. Therefore, this paper aims to study the out-of-plane mechanical properties of tall FC partition walls under static loading. Experimental studies were conducted on the influence of different connection forms, as well as different construction column spacings on the out-of-plane mechanical performance of tall FC partition walls. It can be found that different connection forms had almost no effect on the cracking load. The cracking load decreased gradually with the increasing of the structural column spacings. The specimens with more rigid connection had better crack resistance ability during the service phase. With the increasing of the spacing of structural columns, the restraining effect of the steel skeleton on the FC wall panel, its out-of-plane bearing capacity and stiffness all decreased; The configuration of the steel skeleton reduced the brittleness of FC material; The weak part of tall FC partition wall was in the bonding area between FC wall panel and square steel tube, which should be paid attention to in practical engineering.

Experimental investigation of wind-induced vibration of multi-cross-section steel tube lightning rods in substation

The multi-cross-section steel tube lightning rod (MSTLR) in the substation are susceptible to along-wind buffeting and vortex-induced vibration due to their inherent flexibility, low damping properties and multi-circular-section. This paper conducted a wind tunnel experiment on a 1:5 aeroelastic model of MSTLR under three wind fields with different turbulence intensity (uniform, 4.0%, and 7.0%). The amplitude, PSD, time-frequency curves, frequency components, and trajectory of wind-induced vibration are analyzed by measuring the acceleration responses at different heights and bottom reaction responses in the along-wind and cross-wind directions. A comparison was made between the relevant wind load parameters and those specified in the Eurocode. The results indicate that the distribution of the key participating modes exhibits different patterns with the variance of wind speed and turbulence intensity. Multi-order vibrations and structural coupling in orthogonal directions are observed with total response higher than the Eurocode. With the increase of turbulence intensity from 4.0% to 7.0%, the contribution of turbulence to along-wind acceleration response reaches saturation and has the opposite effects. When the speeds are 21.55 m/s and 27.33 m/s, respectively, the vortex-shedding frequencies of section 2 and section 3 coincide with the second-order natural frequency, and the vortex-induced resonance occurs. Those two vortex-induced resonances lead to a sudden increase in the standard deviation of the cross-wind response.

Study on the Effect of Size on the Surface Wind Pressure and Shape Factor of Wind Load of Solar Greenhouses

Study on the Effect of Size on the Surface Wind Pressure and Shape Factor of Wind Load of Solar Greenhouses

Data-driven aeroelastic analyses of structures in turbulent wind conditions using enhanced Gaussian Processes with aerodynamic priors

Recent advancements in data-driven aeroelasticity have been driven by the wealth of data available in the wind engineering practice, especially in modeling aerodynamic forces. Despite progress, challenges persist in addressing free-stream turbulence and incorporating physics knowledge into data-driven aerodynamic force models. This paper presents a hybrid Gaussian Process (GPs) methodology for non-linear modeling of aerodynamic forces induced by gusts and motion on bluff bodies. Building on a recently developed GP model of the motion-induced forces, we formulate a hybrid GP aerodynamic force model that incorporates both gust- and motion-induced angles of attack as exogenous inputs, alongside a semi-analytical quasi-steady (QS) model as a physics-based prior knowledge. In this manner, the GP model incorporates the absent physics of the QS model, and the non-dimensional hybrid formulation enhances its appeal from an aerodynamic perspective. We devise a training procedure that leverages simultaneous input signals of gust angles, based on random free-stream turbulence, and motion angles, based on random broadband signals. We verify the methodology through analytical linear aerodynamics of a flat plate and non-linear aerodynamics of a bridge deck using Computational Fluid Dynamics (CFD). The standout feature of the presented methodology is its applicability for aeroelastic buffeting analyses, showcasing robustness when handling broadband excitation. Importantly, the non-linear hybrid model preserves its capability to capture higher-order harmonics in the motion-induced forces and remains applicable for flutter analysis, while incorporating both motion and gust angles as input. Applications of the methodology are anticipated in the aeroelastic analysis and monitoring of slender line-like structures.

Scenario-based LCA for assessing the future environmental impacts of wind offshore energy: An exemplary analysis for a 9.5-MW wind turbine in Germany

BackgroundOffshore wind energy (OWE) will play a significant role in achieving climate neutrality. For example, several scenarios for Germany (e.g., Kopernikus base, Kopernikus 1.5 degree, Prognos CN65, and CN60) depict substantial OWE annual installed capacity additions, especially after 2030. This tendency promotes OWE technology development as deployment expands, allowing manufacturers to gain expertise and optimize wind turbine construction. The global trend towards ever-larger components (e.g., hub height and rotor diameter) is critical to achieving higher-rated capacities. These aspects and others, such as wind quality, influence not only OWE annual electricity production but also its environmental performance. In addition, future supply chains might reduce their environmental impacts and enhance OWE climate change mitigation. In this paper, a prospective life cycle assessment (pLCA) is developed and applied exemplarily for a 9.5-MW offshore wind turbine (OWT) on the North Sea coast of Germany for the years 2030 and 2050. Considering that the current OWTs under construction in Europe have an average capacity of 10 MW, Germany plans to instal OWTs of 9.5-MW. This exemplary OWT describes the potential advances for offshore wind turbines in 2030 and 2050, considering component scale-up and learning effects. Yet, the methodology is adaptable to various installed capacities and regions. This approach allows us to analyse not only the potential future characteristics of wind turbines, but also future developments in OWE supply chains. Therefore, relevant parameters related to OWT construction and operation (e.g., rotor diameter, hub height, distance to the shore, lifetime, etc.) as well as prospective life cycle inventory data for background systems that reflect potential future developments in the broader economy are considered. In this way, scenarios (e.g., optimistic, moderate, and pessimistic) for OWE elucidate the expected environmental impacts, such as climate change, marine eutrophication, and abiotic depletion potential, in 2030 and 2050.ResultsThe findings describe the variability of the environmental impacts of a 9.5-MW offshore wind turbine representing the technologies expected to be available in Germany in 2030 and 2050 and show that climate change impacts could vary between 7 and 18 g CO2-eq per kWh produced in 2030 and between 5 and 17 g CO2-eq per kWh in 2050. However, marine eutrophication could experience a significant increase (100% increase), depending on the consideration of hydrogen as a fuel in the electricity mix, as demonstrated in the climate-neutral scenarios adopted for Germany. Overall, construction efficiency improvements in 2050 might reduce the required materials, leading to a 6% decrease in abiotic depletion potential compared to 2030 values.ConclusionsThis paper highlights the need to consider temporal improvements in LCA studies, particularly when assessing the environmental impacts of offshore wind turbines. The complex nature and rapid growth of offshore wind technology require a comprehensive life cycle approach to deepen our understanding of its potential environmental impacts.

Decentralized coordinated optimal dispatching of multi-area interconnected electricity-gas-heat system based on inertia Bregman ADMM

The coordinated interconnection of multi-area interconnected electricity-gas-heat systems (MIEGHS) has become a typical feature of the modern energy internet. While enhancing system operational efficiency, it also introduces complexity and uncertainty into system operation. In consideration of these factors, a decentralized coordinated robust optimization scheduling framework for MIEGHS is proposed to facilitate coordinated optimization. Firstly, a two-stage robust stochastic optimal dispatching model for a single-area integrated electricity-gas-heat system (IEGHS) is established, considering the uncertainty of wind power output and load. Secondly, a decentralized self-regulation control model for MIEGHS is proposed based on the principle of consistency constraints. Next, considering both the timeliness and convergence of the traditional alternating direction method of multipliers (ADMM) in solving problems, an improved ADMM method based on inertial Bregman distance is presented for the optimized solution of the proposed model. Finally, the effectiveness and superiority of the presented model and methods are verified by three interconnected IEGHS.

Experimental investigation and multi-hazard evaluation of viscous outriggers with amplification devices

This study proposes a novel amplified viscous damping outrigger (AVDO) to enhance the energy dissipation efficiency of a viscous damping outrigger (VDO) system. The AVDO combines the VDO with a lever amplification device, significantly enhancing energy dissipation by amplifying damper displacement. A mechanical model of the AVDO was established, and its performance was compared to that of the VDO using model tests. The experimental results demonstrated that the lever device effectively amplified damper deformation. Additionally, the damping force and energy consumption of the AVDO increased by 4.93 and 4.85 times, respectively. The deviation between the experimental and theoretical results was under 10 %, indicating that the mechanical model successfully assessed the AVDO's properties. Finally, a simulation analysis was conducted on a super high-rise structure subjected to seismic and wind loads to verify the vibration control capabilities of AVDO. The vibration-damping efficiency of AVDO was evaluated by comparing the responses of AVDO and VDO. AVDO was found to reduce top acceleration and displacement by 46.5 % and 36.8 %, respectively, under seismic loading. Additionally, AVDO reduced the peak acceleration of the top floor by 39.5 % under wind loading. AVDO effectively enhances the seismic capacity of the structure and improves the comfort of the super high-rise building. It also achieves economic savings of 79.6 % compared to the VDO at the same level of performance.

Aerodynamic optimization of high-rise building with façade ribs through CFD-based multi-objective optimization algorithm

Façade appurtenances is an effective aerodynamic optimization measure for alleviating the wind loads on high-rise buildings in modern cities, while the optimized layout of façade ribs necessary for practical engineering remains unclear. The conventional method through numerical simulations and wind tunnel tests can only obtain limited optimal schemes of ribs, the optimization process is time-consuming and laborious, an optimization algorithm can be used to effectively evaluate the optimal arrangement of façade ribs. In present study, a multi-objective optimization procedure coupling large eddy simulation (LES), back propagation neural network (BPNN), and non-dominated sorting genetic algorithm (NSGA-II) is applied to evaluate the optimal arranged parameters of façade vertical ribs. The optimization procedure can quickly identify the optimal location parameter b and extensional depth d of façade ribs that producing minimum wind loads acting on building and ribs. The findings indicate that there are complex non-linear relationships between the ribs arrangement parameters and the objective wind loads. The mean drag C‾d and fluctuating lift C'l of models of windward ribs and upstream sidewall ribs have opposite trend. The relationships between wind forces and arranged parameters of the downstream sidewall and leeward ribs are relatively complicated due to the vortex shedding. Genetic algorithm NSGA-II can effectively evaluate the optimal trade-off solution among multi-objective wind loads. The ranges of optimal layout parameters b/D and d/D are 0.14–0.17, 0.073–0.077, the ratio of b/d is about 2, and the optimal arrangement of façade ribs well balances the total wind forces on the model and wind forces on the ribs. The 3D numerical simulations demonstrate that the optimal layout of the ribs can considerably improve the flow structure and wind load, the maximum reduction ratio of the C‾d and C'l are achieved 25 % and 56 %, respectively. The obtained optimized layout parameters can provide reference for engineers when actually using the facade ribs.

Experimental study on the influence of turbulence on hail impacts

Hailstorms, characterized by their intensity, are often accompanied by strong winds and heavy rain, posing significant destructive potential. Data indicate that the economic losses caused by hail to buildings, particularly solar panels, have been increasing annually. However, research on the hail resistance of photovoltaic panels has predominantly focused on the isolated effects of hail impacts and wind loads, neglecting the coupling effects between wind and hail. In this study, a device was designed to couple both wind and hail. The effects of turbulence, hail size, and velocity on hail impact behavior were systematically studied and quantified. A predictive formula for the peak load of hail impact on structures was established. The results indicate that the impact of turbulence on hail is significant. When turbulence intensity varies with hail velocity, hail impact force increases as turbulence decreases and hail velocity increases. When both turbulence and hail diameter vary, the impact force of smaller hailstones shows less variation with increasing turbulence. According to variance analysis, hail velocity is the most significant factor affecting hail impact, followed by hail diameter and finally turbulence. The regression equation is given by F=-0.624Iu+5116.25D+7.85Vhail-259.709\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$F = - 0.624I_{{\ ext{u}}} + 5116.25D + 7.85V_{hail} - 259.709$$\\end{document}, where F\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$F$$\\end{document} represents the peak impact force in Newtons (N), Iu\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$I_{{\ ext{u}}}$$\\end{document} denotes the turbulence intensity, D\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D$$\\end{document} is the hail diameter in meters (m), and Vhail\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$V_{hail}$$\\end{document} is the hail velocity in meters per second (m/s).

Experimental and numerical study on dynamic response of a photovoltaic support structural platform with a U-shaped tuned liquid column damper

A tuned liquid column damper (TLCD) is widely used in offshore structures as a passive energy dissipation device to reduce the harm of wind, wave, and current loads to the safety of offshore platforms. This investigation explores the dynamic response and interaction mechanism of a photovoltaic support structural platform (SSP) equipped with a TLCD by experimental and numerical analysis. The vibration mitigation performance of the TLCD under varying liquid depth ratios, external excitation frequencies, and amplitudes is systematically evaluated. The experiments focus on assessing the structural dynamic response and wall pressure to determine the vibration reduction efficiency of the TLCD for structures with fundamental frequencies more than 2 Hz. The experimental results indicate that the TLCD can reduce the structural response maximally near the natural frequency (2.52 Hz) of the structure, with vibration reduction effectiveness ranging from 42.0% to 85.1%. Additionally, one develops a two-way fluid-structure interaction (FSI) model to investigate further the impact of hydrodynamic pressure caused by sloshing inside the TLCD on the SSP motion response, which providing a more detailed explanation for the different phenomena observed in the experimental results.

Dynamic response of OWT tripod pile foundation in clay considering scour

Tripod-supported offshore wind turbine (OWT) foundation must withstand wind, wave, and seismic loads. In addition, it may be threatened by scouring during its service life, which could affect its bearing capacity and the overall OWT dynamic response. This study develops a three-dimensional numerical model of OWT tripod pile foundation to investigate scour effects. The numerical model incorporates a simplified single bounding surface model to simulate the dynamic stress–strain response of clay soil. The results revealed that scouring can reduce the first-order natural frequency of tripod pile-OWT system; however, the reduction usually does not lead to resonance within the 1P frequency range. Nonetheless, as the scour depth increases under wind and wave loads, the horizontal displacement of the wind turbine structure increases monotonously; however, its peak acceleration increases initially then decreases slightly as the scour depth continues to increase. Under seismic loading only, the OWT response exhibits complex evolution pattern as the scour depth increases. On the other hand, the foundation horizontal displacement and rotation angle increase significantly under combined wind-wave-seismic loads when the scouring depth reaches three times the pile diameter. Finally, the scouring depth has a relatively small impact on the foundation vertical displacement.