Wind Loads Research Articles

Land coverage prediction using convolutional neural network for enhanced wind loading estimation

PurposeThe wind loading on a building is likely to deviate further from the known wind loading due to the complexity of the real-world land coverage. To address this issue, research is needed in two separate areas. First, wind tunnel testing needs to be conducted for more complex terrains. Second, research is needed to classify real-world land coverage with high accuracy, specifically for wind engineering applications. This paper deals with this second area of research. The machine learning-based land cover prediction is a promising technique because it can remove subjectivity in human interpretation of upwind terrain.Design/methodology/approachThis paper presents a new deep neural network for land coverage prediction that can distinguish low- and mid-rise buildings in the built environment to enhance the estimation of surface roughness necessary in wind engineering. For the dataset, Landsat 8 satellite images were used. A patch-based convolutional neural network was employed and improved. The network predicted the land coverage at the center of the patch. Two different label schemes were used where the proposed network either achieved better accuracy than the conventional model or recognized additional building types while maintaining a similar level of accuracy.FindingsCompared to the validation accuracy of 78% in a previous study, the proposed method achieved the validation accuracy of 90% thanks to the improvements made in this study as well as the consolidation of labels with similar surface roughness. When additional building categories were added, the validation decreased to 80%, which is comparable to the previous study but is now able to predict different building types.Originality/valueThe improvement of the proposed method will depend on the site characteristics. For the sites tested in this paper, the error reduction in wind speed and pressure was up to about 55%. In addition to more accurate wind speed and pressure, better identification of buildings will benefit wind engineering research, as different building types cause different downwind effects. An example application would be automated recognition of areas that have a certain distance from the target building type to identify downwind areas affected by high winds.

Impacts of Transition Piece Designs on the Resilience of Large Offshore Wind Turbines Subject to Combined Earthquake, Wind and Wave Loads and Soil‐Structure Interaction

ABSTRACTThe urgent global drive to mitigate greenhouse gas emissions has significantly boosted renewable energy production, notably expanding offshore wind energy across the globe. With the technological evolution enabling higher‐capacity turbines on larger foundations, these installations are increasingly situated in earthquake‐prone areas, underscoring the critical need to ensure their seismic resilience as they become a pivotal component of the global energy infrastructure. This study scrutinises the dynamic behaviour of a 15 MW offshore wind turbine (OWT) under concurrent earthquake, wind and wave loads, focusing on the performance of the ultra‐high‐strength cementitious grout that bonds the monopile to the transition piece. Employing LS DYNA for numerical simulations, we explored the seismic responses of four OWT designs with diverse transition piece cone angles, incorporating nonlinear soil springs to model soil‐structure interactions (SSIs) and conducting a site response analysis (SRA) to account for local site effects on ground motion amplification. Our findings reveal that transition pieces with larger cone angles exhibit substantially enhanced stress distribution and resistance to grout damage, evidenced by decreased ovalisation in the coned sections of the transition piece and monopile, and improved bending flexibility. The observed disparities in damage across different cone angles highlight shortcomings in current design guidelines pertaining to the prediction of grout stresses in conical transition piece designs, with the current code‐specified calculations predicting higher stresses for transition piece designs with larger cone angles. This study also highlights the code's limitations when accounting for grout damage induced by stress concentrations in the grouted connections under seismic dynamic loading conditions. The results of the study demonstrate the need for refinement of these guidelines to improve the seismic robustness of OWTs, thereby contributing to the resilience of renewable energy infrastructure against earthquake‐induced disruptions.

Spanwise flow control of bridge deck using Bayesian optimization technique

This study introduces a novel framework in bridge wind engineering, merging Bayesian optimization (BO) with computational fluid dynamics (CFD) to optimize spanwise control parameters for the Great Belt bridge deck. This study leverages the BO framework for an automated, data-driven adjustment of the blow-suction sinusoidal spanwise perturbation (SSP) parameters at the leading and trailing edges of bridge decks. The primary aim is to finely tune the SSP control, stimulating the secondary instability in the spanwise vortices in the wake flow field. This process effectively generates streamwise vortices to suppress the spanwise ones, significantly mitigating fluctuating aerodynamic forces and vortex-induced vibration of the bridge deck, improving its aerodynamic stability. The results demonstrate that the BO framework-driven SSP control method can efficiently reduce the aerodynamic forces while finding the optimal SSP wavelength. Furthermore, through the optimization of multi-parameter variables in SSP control, the optimal combination of amplitudes and wavelengths for the SSP are achieved. Additionally, it was found that blow-suction at the trailing edge of the bridge deck is more effective than at the leading edge.

Structural Analysis of Latticed Steel Transmission Towers Subjected to Nondeterministic Wind Loads

Lattice steel towers are commonly used to support overhead power transmission lines. However, the dynamic behavior of these structures is often overlooked in current design practices. Given that many accidents involving these towers occur even at basic wind speeds lower than those specified in the project, it is likely that dynamic actions play a significant role in these failures. This study proposes a method to accurately simulate the interaction between transmission line cables and towers under non-deterministic wind loads to assess displacements and forces in the steel towers. The study examines a transmission line system consisting of towers, conductors, shield wires, and insulators, featuring a central suspension tower of 32.86 m in height, flanked by two end towers with 450 m spans. Finite element modeling was developed to account for the dynamic characteristics of the wind. Wind loads were modeled as a random process based on their statistical properties. The results revealed significant differences in displacement and force values when comparing the results provided by static and dynamic analyses. The structural design of a base leg member indicated potential failure at higher wind velocities, highlighting the importance of considering the wind dynamic effects in the design.

Structural optimisation of free-swinging agrivoltaic fences

Agrivoltaic fences enable farmers and ranchers to produce energy while maintaining profitable agricultural activity. They consist of vertical posts between which vertical solar panels are mounted. A significant part of the structural costs of these frames comes from their high wind load, which requires large diameter posts, often with wind bracing, and substantial foundations. This research focuses on free-swinging agrivoltaic fences, a new concept that allows panels to 'float' in the wind, an akin to clothes drying on a clothesline. In other words, the panels are suspended from hinged joints, allowing them to swing in strong winds. This study demonstrates that the internal forces in the posts are more than 8 times lower than those induced by fixed vertical panels and scales various parameters involved such as the height of the system, the wind force acting on the panel, its dimensions and weight. The results highlight the fact that the maximum forces generated in the posts of such a system are independent of the wind model considered and can be determined using only the weight of the panel, the height at which it is fixed and the position of the wind pressure on the panel's surface. Finally the study provides a much more reliable and safer design methodology than that used for vertical fixed panels. Design curves are established to provide designers with guidelines on what type of section to use, whether it is steel or timber.

Assessment of Building Nondeterministic Dynamic Structural Behavior considering the Effect of Geometric Nonlinearity and Aerodynamic Damping

The objective of this research is to evaluate the dynamic structural response of tall buildings subjected to wind loads, taking into account the influence of geometric nonlinearity and aerodynamic damping. The project focuses on a steel-concrete composite structure with 48 floors and a height of 172.8 m, examining its response to wind non-deterministic dynamic actions. The building finite element model was developed based on the Finite Element Method (FEM), using the ANSYS computational program, and considering the soil-structure interaction effect, with the objective of obtaining a realistic representation of the dynamic behavior. The building dynamic response was obtained based on the displacement and acceleration values, determined with the consideration of a wind velocity range between 5 m/s (18 km/h) and 45 m/s (162 km/h). The findings of this study indicate that when the effect of geometric nonlinearity was incorporated into the analysis, the dynamic response of the investigated building exhibited notable discrepancies. The maximum differences observed in the horizontal translational displacements and accelerations were 30% and 45%, respectively. In contrast, the inclusion of aerodynamic damping had a negligible impact on the structural dynamic response, with maximum differences of 5% for displacements and 10% for accelerations.

3D printing of a multi-performative building envelope: Assessment of air permeability, water tightness, wind loads, and impact resistance

This study investigated the 3D printing feasibility of mono-material facade panels with recycled thermoplastic. The design had integrated performance parameters, namely air permeability, water tightness, resistance to wind loads, and impact resistance, and fabrication parameters in a computational iterative process to inform the geometry topology. The fabrication parameters were integrated and evaluated for geometry accuracy, print path accuracy of 5 mm length, overhang higher than 45°, inner layer adhesion, and adhesion to the print bed. Two panels, measuring 1.6-meter length and 2-meter height, and six connections were fabricated and evaluated in a standardized facade testing rig. The air permeability displayed a larger than 1.5 m3/m2·h permissible Class 1 value due to air gaps in the manufactured panels. The same gaps that occurred during the fabrication process permitted water flow in both panels after 7 minutes of testing. The panels passed standardized serviceability and safety standards for wind load resistance and achieved a maximum E5 class for impact resistance. The structural strength values were 1500 Pa for serviceability, 2250 Pa for safety load, and 3262 Pa for breaking load. These findings demonstrated that 3D-printed geometries have a high potential to facilitate sustainable design strategies by integrating multiple performances within a mono-material building envelope.

On the design and behavior of axially-compressed square concrete-filled double-skin tubular short columns for ocean engineering applications

Deep-sea offshore wind technology development is now deemed a strategic national need in China. At the same time, research and engineering communities have a substantial increase in intertest on the design and behavior of novel arrangements for double-skin composite columns. Accordingly, concrete-filled double-skin steel tubular (CFDST) columns have recently gained significant importance in wind farm support structures as well as tall buildings with heavy loads. To predict the axial compressive resistance of square CFDST short columns with square inner tubes (SS-CFDST) or circular inner tubes (SC-CFDST), a new design resistance model has been proposed in this paper. First, test data for axially-loaded short columns of SS-CFDST and SC-CFDST configurations were extracted from literature studies. Then, available design resistances in the European and American specifications, as well as from previous studies, were examined, and a range of accuracy results were displayed. Subsequently, new formulae for determining the lateral confining pressure (frp) supplied by outer and inner tubes in different types of square CFDST columns have been developed using the data gathered from the experimental tests. A new design resistance model has then been proposed to calculate the axial compressive resistance of SS-CFDST and SC-CFDST short columns, based on the proposed formulae for frp in addition to the confined concrete strength. This has been followed by a finite element (FE) modeling using ABAQUS program that has been well validated, generated to increase the resistance data of these columns. The design formula was then verified through the extensive parametric studies generated by the FE modeling. According to the comparisons between numerical and proposed resistances, the design proposal was found to yield more accurate and reliable results in terms of the average resistance ratio, accuracy across the whole range of the relative tube slenderness ratio and the calculated reliability index.

Recursive Bayesian estimation of wind load on a monopile-supported offshore wind turbine using output-only measurements

Offshore wind turbine structures experience combined wind and wave loading during their lifetime, and the cyclic characteristics of these loads significantly impact the fatigue life of the support structure. Continuous monitoring of stress-related quantities, such as strain time histories at hotspot locations of the structure, can help to estimate the fatigue life. However, sparse measurements from the substructure necessitate using a digital twin as a tool for structural health monitoring by creating a virtual model. This virtual model relies on real-time input loads for virtual sensing and stress-related quantities prediction. However, the exact loading on these structural systems is often unknown or estimated with considerable uncertainty. This paper implements a recursive window-based Bayesian estimator for input load estimation and virtual sensing of acceleration and strain time history at unmeasured critical locations using output-only measurements. The estimator is numerically and experimentally validated in the context of input load estimation for an offshore wind turbine, and the results are compared with a traditional augmented Kalman filter and a linear regression approach for the quasi-static component of loading. The method is first demonstrated through a numerical study using a finite element model of a 6 MW offshore wind turbine, where input wind load time histories are accurately estimated. Then, the framework is applied to the real data measured from an offshore wind turbine in the North Sea. The study demonstrates the window-based Bayesian input estimator as a promising tool for the digital twinning of offshore wind turbines, demonstrating superior accuracy in input load estimations and full response predictions compared to the augmented Kalman filter and linear regression methods without the constraint of collocated measurements at input load locations.

Dynamics Performance Research and Calculation of Speed Threshold Curve for High-Speed Trains Under Unsteady Wind Loads

Affected by strong wind environments, the vibration of trains will significantly intensify, which will severely impact the running quality of trains. To address such challenges, an improved wind load model is proposed in this paper to simulate the shock of strong wind on trains. The proposed model employs the integral approach to calculate the equivalent wind load on trains and applies it to the body of trains during the dynamics simulation process. Eventually, the two-level running quality threshold curve for passenger and freight trains is acquired through the conditional probability density function and the regularized regression model. This achievement covers train speed restrictions for wind speeds ranging from 0~25 m/s, providing a scientific basis for railway departments to adjust train speeds based on real-time wind speeds. It is of utmost importance for ensuring the safe and efficient operation of trains under strong wind conditions.

Cratylia mollis lectin reduces inflammatory burden induced by multidrug-resistant Staphylococcus aureus in diabetic wounds.

In diabetes, tissue repair is impaired, increasing susceptibility to Staphylococcus aureus infections, a pathogen commonly found in wounds. The emergence of S. aureus strains that are highly resistant to antimicrobial agents highlights the urgent need for alternative therapeutic options. One promising candidate is Cramoll (Cratylia mollis seed lectin), known for its immunomodulatory, mitogenic, and healing properties. However, its efficacy in infected diabetic wounds remains unexplored. This study evaluated the effects of topical Cramoll treatment on diabetic wounds infected by S. aureus. Diabetic Swiss mice (induced by streptozotocin) were subjected to an 8-mm wound on the back and subsequently infected with a suspension of multidrug-resistant S. aureus. During the treatment period, the wounds were clinically evaluated for inflammation and the area of injury. After seven days, samples were collected from the wounds to quantify the bacterial load and histopathological and immunological analyses. Wounds infected by S. aureus exhibited more pronounced areas and severity indices, which were significantly reduced by Cramoll treatment (p < 0.05). Histopathological analysis revealed a reduction in inflammatory cells and an increase in revascularization with Cramoll treatment (p < 0.05). Cramoll also promoted greater collagen production compared to controls (p < 0.05). Furthermore, Cramoll treatment significantly reduced the S. aureus load in wounds (p < 0.0001), decreased TNF-α and IL-6 levels in infected wounds, and increased ERK pathway activation (p < 0.05). In conclusion, Cramoll lectin improves the healing of diabetic wounds, and these results contribute to the understanding of Cramoll healing mechanisms, reinforcing its potential as a healing agent in various clinical conditions.

Joint Probability Distribution of Extreme Wind Speed and Air Density Based on the Copula Function to Evaluate Basic Wind Pressure

To investigate an appropriate wind load design for buildings considering dynamic air density changes, classical extreme value and copula theories were utilized. Using wind speed, air temperature, and air pressure data from 123 meteorological stations in Shandong Province from 2004 to 2017, a joint probability distribution model was established for extreme wind speed and air density. The basic wind pressure was calculated for various conditional return periods. The results indicated that the Gumbel and Gaussian mixture model distributions performed well in extreme wind speed and air density fitting, respectively. The joint extreme wind speed and air density distribution exhibited a distinct bimodal pattern. The higher the wind speed was, the greater the air density for the same return conditional period. For the 10-year return period, the air density surpassed the standard air density, exceeding 1.30 kg/m3. The basic wind pressures under the different conditional return periods were more than 10% greater than those calculated from standard codes. Applying the air density based on the conditional return period in engineering design could enhance structural safety regionally.

A comprehensive analysis of the tail-dependent structure of wind loads and its engineering applications

Wind load field characteristics on the roof surface of low-rise buildings based on field measurements have crucial engineering guidance value. In the background, tail-dependence structure from measured wind loads can assist in modeling the joint tail distribution of multivariate wind loads. In this study, the non-parameter estimation method, multi-copula function model and multivariate peak over threshold model are applied to estimate its precise value. The upper tail dependence coefficient's value is around 0.20 when the quantile for p(y) = 0.75. When p(y) = 0.95, the Gumbel copula overestimates the tail-dependence value slightly. Additionally, the lower tail-dependence values estimated by the Clayton copula are around 0.19 at 0.25 quantile. For extreme tail-dependence coefficients, little difference exists in the estimated results by the non-parameter estimation method and the peak over threshold model, in which its value varies from 0.80 to 0.90. Under roof pitch = 5°, its value exhibits some dispersion at different locations. An area weight function is applied to estimate the extreme tail-dependence value between critical regions. Then, the expectation function of tail dependence reaches the peak value in p(x) = 0.50, p(y) = 0.50 and it has different gradients for different variables and tail regions. Additionally, the lower tail dependence structure is significantly stronger than the upper tail dependence for wind loads with negative skewness. For application in wind engineering, potential applications in risk analysis for roof structures, extreme value estimation for local region block wind load, and wind load forecast for unmonitored locations are proposed.

Investigation of wind load characteristics of cantilevered scaffolding of a high-rise building based on field measurement

Over recent years, rigid porous plates with higher wind resistance coefficients have become more frequent in construction projects, replacing flexible dense mesh safety nets. This change has resulted in a substantial increase in the load on the surface of the clad scaffolding. The paper is centered on the characteristics of wind load on the cantilever construction scaffolding of a high-rise building in Xi’an, with the objective of concluding the distribution rules by field measurement. The study revealed that the non-Gaussian characteristics of wind pressure are most pronounced near the incoming separation point and the middle of the building surface. The local wind force coefficient adheres to a logarithmic distribution pattern with the wind pressure turbulence. The turbulence, gust factor, and skewness and kurtosis of fluctuating wind pressure exhibit an “S-like” distribution along the building surface. Based on the research findings, as the wind pressure increases significantly, two correlations between the mean value of the fluctuating stress and fluctuating wind pressure were identified: linear and mean fluctuation.

STAAD Based G+2 Single-Column Residential Analysis

The principle cause of this study is to layout a whole building relaxation on a single column. The rapid increase in population and scarcity of land tends to the development of construction technology and high- rise commercial structures. The building plays a vital role in improving various activities in the late world. The Aim of present study “Analysis and design of high rise building by staad pro is to define proper technique for creating Geometry, cross sections for column and beam etc, developing specification and supports conditions, types of Loads and load combinations. In this study a 30- storey high rise structure is analyzed for seismic and wind load combination using staad pro and comparison is drawn. Currently, there are four mosques on Java Island recognized as Saka Tunggal Mosques, which employ a single wooden column as the main column, placed at the center of the prayer hall to support the roof. This unique structural system, when compared to the traditional four-column system, is remarkable even if its style is exceptional for mosques on Java Island. This study aims to provide scientific data and promote the local government's understanding about the importance of the Saka Tunggal Mosques by focusing on the one in Banyumas, which is placed at a cultural heritage site, founded in 1871. The rapid increase in population and scarcity of land tends to the development of construction technology and high-rise commercial structures. Building plays a vital role for improving the various activities. In the late world, prompt to action of peoples from one place to another is of great extent mainly for earnings. In building more facilities like financing section, computer section, administration section, design section and drawing section are provided. The aim of the project is to analyse and design of multi-storey building resting on the single column by using different code provisions. A lay out plan of the proposed building is drawn by using AUTO CADD. The structure consists of ground floor plus five floors, each floor having the one house. Staircase must be provided separately. The planning is done as per Indian standard code provisions. The building frames are analyzed using the various text books. Using this so many standard books analysis of bending moment, shear force, deflection, end moments and foundation reactions are calculated. Detailed structural drawings for critical and typical R.C.C. members are also drawn. Recent studies regarding progressive collapse resistance of buildings considered only single critical column removal scenario. However, limited investigations have been conducted so far to assess multi-column removal scenarios. Hence this study is made to compare progressive collapse resistance of a multi-story building under both single and multi-column removal scenarios. An eight-storey reinforced concrete building was analyzed by using linear static analysis procedure and DCR values of the members are calculated to investigate the potential of progressive collapse as per GSA guideline.

Dynamic response analysis of monopile-supported offshore wind turbine on sandy ground under seismic and environmental loads

Monopiles are the most widely adopted foundation type for Offshore Wind Turbines (OWTs) in shallow waters. With the expansion of the construction of OWT, the number of OWT farms in seismic regions increases globally including the coastal areas of Japan and China. It is necessary to evaluate the impact of earthquakes including the vibration and soil liquefaction on the OWTs supported by the monopile foundation, while the effects of liquefaction on offshore structures, especially for OWTs with monopiles, have not been sufficiently studied. This study investigates the seismic response of the monopile-supported OWTs with the use of an advanced soil model. A three-dimensional numerical model is built, and dynamic analyses are carried out using the OpenSees framework. The pressure-dependent multi-yield (PDMY03) constitutive model is used to simulate the dynamic soil behavior. The applicability of the large-diameter pile modeling method for proper soil-pile interaction modeling in this numerical analysis is first validated through centrifuge tests on monopiles subjected to lateral loading. The dynamic analyses are then carried out to demonstrate the seismic response of the entire OWT system. The numerical results indicate that the contribution of higher modes of vibration is becoming of increased importance for large wind turbines and soil-structure interaction plays a significant role in the dynamic response. Moreover, the monopile-supported OWT in dense sand deposits experiences substantial lateral displacement and rotation under the combined action of wind and earthquake loads when liquefaction occurs.

The response characteristics and stability evaluation of vegetated slope under strong wind

As one of the major geological disasters in southeastern China, typhoon-induced vegetation slope instability causes significant loss of life and property each year. Despite the criticality of this issue, the response mechanism of vegetated slopes to wind loading in terms of soil deformation and stability still remains unclear. This research conducted field investigations on 330 historical landslides in Yongjia County, Zhejiang Province, analyzing their spatiotemporal distribution and developmental characteristics to establish a conceptual model. The influence of wind and vegetation conditions on slope dynamic parameters and soil strength parameters were subsequently determined through numerical simulations using FLAC3D software, model tests, and direct shear tests. The results show that: (1) The influence of wind on the dynamic response of vegetated slopes is significantly affected by wind speed. At wind forces ≤ 12 (hurricane: 32.7–36.9 m/s), vegetation plays a positive role in enhancing slope stability. At wind forces ≥ 13 (typhoon: 37.0–41.4 m/s), vegetation exerts a negative influence under the combined action of strong wind loads. (2) Based on the experimentally determined evolution of soil strength parameters, a formula c (v, w) was fitted to express the variation of cohesion with wind speed (v) and moisture content (w). (3) The optimized evaluation model demonstrates increased sensitivity compared to the traditional model, resulting in a 17.88% increase in sliding force and a 10.62–11.64% increase in anti-sliding force. This research accounts for both the direct and indirect effects of wind loading on vegetated slopes. The findings are expected to enhance the stability assessment of vegetated slopes under strong winds and facilitate the development of more accurate machine learning and statistical models in the future.

Aerodynamic and codification study of low-rise buildings: Part I – Fully elevated structures

Elevated residential buildings are widely used in cyclone- and hurricane-prone coastal regions, such as Australia and the United States, as an effective solution to mitigate both storm surge damage and the impacts of extreme winds. The recent edition of ASCE 7–22 introduced wind design provisions for elevated structures for the first time, but these provisions remain under ongoing refinement. This study aims to assess the adequacy of the current ASCE 7–22 wind pressure coefficient provisions for elevated structures by conducting large-scale boundary layer wind tunnel tests at FIU's Wall of Wind Facility. The tests explored the aerodynamics of elevated buildings with varying heights and aspect ratios. Eight 1:10 scale gable-roof buildings were constructed based on post-hurricane damage reports, and peak pressure coefficients (GCp) were estimated for the floor, roof, and walls. These values were compared against the existing ASCE 7–22 provisions, revealing a significant underestimation of the external pressure coefficients. Based on the results, this study proposes increasing the GCp boundaries of specific zones by 50%–127% and introduces two new floor zones for more accurate estimation of wind pressure coefficients on elevated buildings. These findings have broad implications for improving the wind performance of elevated structures, particularly in cyclone- and hurricane-prone regions globally. It is envisioned that the results of this study, along with those in the companion paper, will be considered by the ASCE 7 Subcommittee on Wind Loads for potential inclusion in the next edition of ASCE 7–28, contributing to more resilient building designs.

Calibration of pressures measured via tubing systems: Accounting for laboratory environmental variations between tubing response measurement and wind tunnel testing

Accurate pressure measurements on structures via tubing systems during wind tunnel tests are crucial for precise estimation of wind loads. While calibration studies have traditionally focused on the contribution of tubing configuration to pressure distortion, they often overlook the effects of environmental parameter changes between the measurement of tubing response and aerodynamic pressure on structures. However, higher atmospheric pressure and lower ambient temperature can substantially increase tubing response distortion. To address this, this study introduces a dynamic calibration approach that accounts for such laboratory environmental changes. This method integrates the experimental transfer function, obtained under specific environmental conditions, with numerical estimates of the impact of environmental changes, to derive transfer functions for the desired environmental conditions. The effectiveness of this approach was validated using experimental and numerical transfer functions under two distinct environmental conditions. A case study for outdoor open-circuit laboratories revealed that neglecting environmental conditions during dynamic pressure calibrations could lead to overall average deviations in peak pressures across the channels on a building face of up to ≈ 5%, with local maximum deviations reaching ≈ 10%, respectively. Therefore, the proposed calibration method can significantly enhance the accuracy of pressure measurements via tubing systems, particularly when the tubing response and the pressures are measured under different environmental conditions.

Fatigue study of unbonded flexible risers for ocean thermal energy conversion based on the joint distribution of wind, wave, and current

This paper investigates flexible risers attached to the base of a semi-submersible platform. Using meteorological and oceanographic data, the wind-wave-current boundary distribution was fitted, and the c-vine copula method established the joint probability density function of wind, wave, and current. An improved grid-based method was used to account for these loads, selecting conditions that meet the confidence level by calculating occurrence probabilities. Time-domain analysis yielded the flexible riser stress time history, and the Miner linear damage accumulation method calculated damage at critical points. The overall lifespan pattern of the riser was analyzed with the joint probability distribution. Results indicate that large heave response amplitude and higher current speeds significantly reduce the riser's fatigue life. The improved grid-based method effectively reduces computational load, providing a feasible approach for designing the fatigue life of ocean thermal energy conversion risers under wind, wave, and current loads.