Design Wind Speed Research Articles

Impacts of Hurricane Dorian on the Bahamas: field observations of hazard intensity and performance of the built environment

ABSTRACT On September 1 2019, Hurricane Dorian made landfall in Elbow Cay in the Bahamas with sustained winds of 295 km/h and a central pressure of 910 mb, with subsequent landfalls in Marsh Harbour and Grand Bahama Island, where it stalled for two days. This paper presents field observations of Dorian’s coastal hazards and impacts on the built environment in these locales, collected by the Structural Extreme Events Reconnaissance (StEER) Network. Data were collected using a mixed methodological approach: (1) surveying high-water marks and inundation extent, including an approximately 8 m high water mark in Marsh Harbour, (2) conducting surface-level forensic assessments of damage to 358 structures, and (3) rapidly imaging 475 km of routes using street-level panoramas. Field observations are complemented by a debris field analysis using high-resolution satellite imagery. Observed performance reiterates the potential for well-confined, elevated construction to perform well under major hurricanes, but with the need to codify such practices through the addition of storm surge design provisions and an increase in the design wind speeds in the Bahamas Building Code. This study further demonstrates the value of robust reconnaissance infrastructure for capturing perishable data following hurricanes and making such data rapidly available using publicly accessible platforms.

Comparison of Wind Tunnel Test Data for Low-Rise Buildings with Main Wind Force Resisting System Design Procedures

The adequacy of the directional and envelope procedures for the design of the main wind force resisting system is not well understood. The purpose of this study is to evaluate the directional and envelope procedures based on wind tunnel test data for a set of low-rise enclosed buildings with gable-shaped roofs in open terrain (Exposure C). The base shear force and the conditional reliability index are used to determine the adequacy of the procedures. The base shear was compared to the design base shear in each direction based on the horizontal component of the wind load on the wall and roof. The reliability index, β conditional on the occurrence of the design wind speed was computed for a range of system capacities. The main findings are (1) the directional procedure produced a larger design base shear compared to the envelope procedure, primarily due to the difference in external pressure coefficients, (2) the directional procedure provided a higher β, and (3) the envelope procedure provided a β that did not meet the standard target β equal to 3.0 for the main wind force resisting systems with low variability in capacity, but neither procedure met the standard target β for the main wind force resisting systems with high variability in capacity.

Numerical Simulation of Wind Waves and calculation of planning wave factors in the East Taihu Lake, Jiangsu Province, China

Taihu Lake is a large shallow lake in the lower Yangtze River Delta. The wave action in Taihu Lake plays an important role in coastal port construction. In this paper, based on the 10 min average wind speed at 10 m above the water surface recorded hourly from August 14 to August 17, 2014, the SWAN wave model is used to simulate the wind waves of the Taihu Lake in the corresponding period. Due to the lack of long-time series of wave observation data in the project area, the relationship between design wind speed and wind wave is used to calculate wave elements in different return periods. The results show that the strong wind direction and strong wave direction of the East Taihu Lake are NNW. The waves in the proposed Qidu harbor are mainly from the waves outside the permeable breakwater. Under the action of the most unfavorable wave direction NE, the effective wave height of most waters in the harbor is below 0.4m, which can meet the requirements of avoiding waves for fishing boats.

Extreme wind climate of the Arabian Peninsula characterized by using WRF simulation

Wind hazard is one of the most severe natural hazards. Structures and infrastructure can be vulnerable to wind load effects due to extreme wind speeds. Mitigation and the reduction of wind-related risks of structures and infrastructures can be made by considering the wind load effects within the structural design process. Building design codes or standards for some countries in the Arabian Peninsula do not formally define the wind load effects. For countries with wind load provisions in their building codes and standards, the spatial resolution of design wind speeds may not be sufficient to cover many cities or areas. To date, there has not been a comprehensive study on the extreme wind hazards at the design level in the Arabian Peninsula. Extreme wind hazards have been conventionally evaluated by using historical surface observations. However, an investigation showed that many meteorological stations in the Arabian Peninsula cannot be used to evaluate the design wind speeds due to low data quality or insufficient sampling resolution. This study used the Weather Research and Forecasting (WRF) model to obtain data with a high spatial-temporal resolution. The simulated extreme wind speeds across the Arabian Peninsula were characterized statistically. Spatial distributions of the extreme wind speeds and their associated attributes were investigated. The simulated wind speeds were separated into convective event-induced wind speeds and synoptic wind speeds to obtain the design wind speeds. The convective wind events were identified using a statistical algorithm defining the threshold values of the Lifted Index and the Convective Available Potential Energy values. A numerical parametric cyclone model was used to simulate the cyclone-induced extreme wind speeds for the southern coastal regions of the Arabian Peninsula. The design wind speeds were evaluated by using the most appropriate probability distribution and preferred fitting method. Contour maps of various return period wind speeds were developed.

Wind turbine tower failure analysis and wind-induced vibration control

Wind energy has great potential for development in clean energy. The economic loss caused by the destruction of the wind turbine tower in a wind turbine failure is very huge. Therefore, this paper analyzes the gray correlation between the tower damage type and the cause of the damage. The results show that storms, pitch system failure, and wind speed exceeding the design wind speed have a good correlation with the tower damage type. In a storm environment, the dynamic response of the tower top of the wind turbine tower is relatively large, even leading to the overall collapse of the tower. The tuned mass damper (TMD) has an obvious damping effect on the wind vibration response of the tower.

Analysis of the Duration of High Winds During Landfalling Hurricanes

The duration of wind storms over a threshold wind speed value is known to be an important parameter in determining damage and losses, with losses tending to increase with the duration. This is because peak pressures tend to increase with longer duration, many building components and cladding systems are vulnerable to different types of fatigue mechanisms, and the yielding of linear elastic materials in the plastic range depends on the number of load cycles. A hurricane model was used to examine the duration of high winds in the United States at Miami, Galveston, and Charleston with the goal of establishing duration statistics for hurricanes as a function of peak wind speed. It was found that the duration of high winds, defined as the time that the 10 min wind speeds are within 30% of the peak 10 min wind speed, had a significant variation with a range from tens of minutes to more than 20 h, depending on location. The median duration ranged from 1.5 to 4 h at the three locations, depending on location and the design wind speed level (i.e., the risk Category of the building). These results were used to establish a simple normalized model for wind speed as a function of time, which could be used together with the design wind speed to establish load cycles for design.

Tornado-resisting design speeds of nuclear power plants in China

More and more nuclear power plants are being constructed in China, while the nationwide intensity regions with tornado-resisting design speeds are not specified. With the development of tornado damage investigations, more records of tornado events have been accumulated, which makes it possible to establish the probability distribution model of tornado speed and predict the design wind speeds of nuclear power plants. This paper summarizes the derivation of probability distribution of tornado speed based on the parameters of mean occurrence rate, intensity rating, path length and width. The tornado events in China are introduced, while the geographical distribution of tornadoes is described. The mean occurrence rates for each local region with square of 1° longitude and latitude are obtained by moving average method. The records of tornado events, which experienced post-disaster investigations and scattered in research articles, dissertations and yearbooks, are collected and revaluated. Using the accepted tornado records, both the probability distribution of path area and the joint probability distribution between tornado speed and path area are established. The equivalent speeds corresponding to different annual exceedance probabilities are calculated. The suggestions of intensity regions for tornado-resisting design of NPPs in China are proposed. The uncertainties of design wind speeds are simulated by Monte Carlo simulation method. It is indicated that the most significant impact on the uncertainties of design speeds originates from the variation of equivalent speed.

Determining the reference basic wind speed in Ethiopia and comparing with compulsory Ethiopian standard CES 145, 2015

In recent years, Ethiopia’s construction sectors were boost up due to modernization and industrialization. Wind speed data is prerequisite in designing of high raise buildings. In Ethiopia, the most common practice is to adopt design recommendations from European codes of practice which can be quite inappropriate due to the differences in climatical and topographical conditions. To foreground the present condition in Ethiopia, this paper tried to obtain the basic wind speed for different stations/towns. The basic wind speed data which is obtained from 159 stations are then compared with the design wind speed of 22 ​m/s according to ECS 145, 2015. Consequently, a basic wind speed zone map was prepared. The map was developed based on the basic wind speeds evaluated from the annual maximum records collected from each station. Hydrognomon Pythia-statistical analysis was done for different probability distributions. After their calculation the best fitting distribution between empirical and theoretical data was chosen using Kolmogorov-Smirnov test. The findings are clearly showing that the magnitude of the operating basic wind speed was increased in 14–150% from the constant of 22 ​m/s. By using best fitted probability distribution methods of each stations, obtained result are ranging from 25 to 55 ​m/s in Ethiopia.

Estimation of directional design wind speeds via multiple population genetic algorithm

The implementation of the probability analysis method on extreme wind loads considering the directionality and uncertainties of the wind load effect coefficients and wind speeds can yield accurate design wind loads. However, it is difficult to popularize this method among structural designers because its theory and calculation process are complicated. The directional design wind speeds for a given city, which are more suitable in the commonly used simplified method for estimating the wind loads (i.e., the sector-by-sector method), are obtained in this study via multi-parameter optimization. A multiple population genetic algorithm program is established for optimization based on the time histories of the wind pressure coefficients obtained from numerous wind pressure taps of different rigid models. For different structural aerodynamic characteristics, the proposed directional design wind speeds can be combined with the sector-by-sector method to obtain results that are closest to the overall reference values of the design wind pressures of all pressure taps under a certain safety guarantee. The applicability, economy, and safety of the sector-by-sector method with the proposed directional design wind speeds are discussed in comparison to other simplified estimation methods using examples of Des Moines, IA, USA, and Shanghai, China, for non-typhoon and typhoon-prone climates, respectively.

The flow fields generated by stationary and travelling downbursts and resultant wind load effects on transmission line structural system

In many non-cyclone areas around the world, severe thunderstorm downbursts can produce annual gust peaks that are the design wind speeds of general structures, and the resultant wind loads pose a major potential threat to critical infrastructure, such as transmission line structural system. The flow fields generated by downbursts are different from those by the synoptic winds in the atmospheric boundary layer. In order to obtain a wind load model of downburst, scholars have made many attempts to study the flow characteristics of downburst-like events. However, in previous studies, the effects of different experimental setup parameters on distribution of downburst wind speed have not been fully discussed. In this paper, an experimental study is conducted using a pulsed wall jet experimental simulator located at Tohoku University, Japan, to analyse the flow fields of stationary and travelling downbursts, and the resultant wind load effects on transmission line structural system. The comparison results show that different experimental settings will affect the maximum wind speed obtained and the height providing the maximum wind speed. The translational speed ratio defined by the ratio of moving speed to jet inlet speed will affect the wind speed distribution in the longitudinal direction of the generated flow field of the travelling downburst. In addition, the comparative studies show that the wind speed distribution of travelling downburst cannot be simply expressed as the vector sum of stationary downburst wind speed distribution and the jet moving speed, and that speed of the travelling downburst can intensify the non-uniform wind loading relaying to the transmission line structural system. For the analysis of the downburst flow fields, a multi-degree-of-freedom analysis is needed to consider its three-dimensional effect, that is, the distributions of wind speeds along the three coordinate axes, and the comprehensive effects of influencing parameters.

Stability behavior of the transmission line system under incremental dynamic wind load

Wind load is the principal cause for a large number of the collapse of transmission lines around the world. The transmission line is traditionally designed for wind load according to a linear equivalent method, in which dynamic effects of wind are not appropriately included. Therefore, in the present study, incremental dynamic analysis is utilized to investigate the stability behavior of a 400 kV transmission line under wind load. In that case, the effects of vibration of cables and aerodynamic damping of cables were considered on the stability behavior of the transmission line. Superposition of the harmonic waves method was used to calculate the wind load. The corresponding wind speed to the beginning of the transmission line collapse was determined by incremental dynamic analysis. Also, the effect of the yawed wind was studied to determine the critical attack angle by the incremental dynamic method. The results show the collapse mechanisms of the transmission line and the maximum supportable wind speed, which is predicted 6m/s less than the design wind speed of the studied transmission line. Based on the numerical modeling results, a retrofitting method has been proposed to prevent failure of the tower members under design wind speed.

A design and performance prediction method for small horizontal axis wind turbines and its application

<abstract> <p>The paper deals with small wind turbines for grid-independent or small smart grid wind turbine systems. Not all small turbine manufacturers worldwide have access to the engineering capacity for designing an efficient turbine. The objective of this work is to provide an easy-to-handle integrated design and performance prediction method for wind turbines and to show exemplary applications.</p> <p>The underlying model for the design and performance prediction method is based on an advanced version of the well-established blade-element-momentum theory, encoded in MATLAB™. Results are (i) the full geometry of the aerodynamically profiled and twisted blades which are designed to yield maximum power output at a given wind speed and (ii) the non-dimensional performance characteristics of the turbine in terms of power, torque and thrust coefficient as a function of tip speed ratio. The non-dimensional performance characteristics are the basis for the dimensional characteristics and the synthesis of the rotor to the electric generator with its load.</p> <p>Two parametric studies illustrate typical outcomes of the design and performance prediction method: A variation of the design tip speed ratio and a variation of the number of blades. The predicted impact of those parameters on the non-dimensional performance characteristics agrees well with common knowledge and experience.</p> <p>Eventually, an interplay of various designed turbine rotors and the given drive train/battery charger is simulated. Criterions for selection of the rotor are the annual energy output, the rotor speed at design wind speed as well as high winds, and the axial thrust exerted on the rotor by the wind. The complete rotor/drive train//battery charger assembly is tested successfully in the University of Siegen wind tunnel.</p> </abstract>

Theoretical Analysis of the Bladeless Wind Turbine Performance

A bladeless wind turbine utilizes vortex formation to extract energy from the wind. Vortex formation are small swirls of air which occur as a result of the geometric shape of the device. This study designed a bladeless wind turbine which incorporates a structural support at a distance offset from the center axis of the cylindrical mast. Springs were added to the final design as means to provide the stiffness required to obtain resonance with the vortex shedding frequency and to also assist in supporting the structure. The analysis was conducted at wind speeds 1m/s, 4m/s and 7m/s, where the geometrical properties of the device remained constant. MATLAB was used to analyze the equation of motion derived for the device. The variables of interest in the studies were mainly the angular acceleration, power coefficient and the resonant frequency. The results obtained showed that for wind speeds above and below the designed wind speed of 4m/s the angular velocity remained the same. Results of this model showed that high amplitudes occur only at resonance. Results showed that with the current power generating mechanism, the average efficiency attainable is approximately 2% at steady state. This is the theoretical efficiency which could be achieved based on the current model. It was discovered that for linearly tapered cylinders, increased oscillations occurred during the ‘lock-in range’ for a range of reduced velocities. The reduced velocity of the designed wind speed is approximately Vr = 5m/s. This value lies within the theoretical range lock in range where increased oscillations are expected to occur between reduced velocities of 4.75m/s and 8m/s [1].

Typhoon track simulations in the North West Pacific: Informing a new wind map for Vietnam

This paper addresses the need to revise the current Vietnamese design wind map by proposing a new typhoon wind map for the country, based on Monte Carlo simulations of typhoon tracks in the North West Pacific basin. Using historical typhoon data from the period 1951 to 2019 provided by the Japanese Meteorology Agency, novel multi-variate regression models are proposed for typhoon translation and intensity. Simulations are performed for a 10 ​000 year period and 1-in-50 year extreme wind speeds at gradient height are estimated to create the proposed typhoon wind map. The proposed simulation method is validated by comparison with existing wind codes for China and Hong Kong, and with other simulations and modelling in the literature. The design wind speeds obtained from the current simulations compare well with the Chinese (differences in the range 0%–14%) and Hong Kong (less than 5%) code predictions for various cities in China. While the proposed wind map with a finer geographic granularity agrees well with the current Vietnamese wind code for most areas affected by typhoons, there are notable differences for areas subjected to the strongest typhoon winds, emphasising the need for a revision of the code.

Comparative Assessment of Different Modelling Schemes and Their Applicability to Inland Small Reservoirs: A Central Europe Case Study

Sustainable landscape management involve also water reservoir management. The demand of their reconstruction represents a good opportunity for redesigning hydrotechnical structures and their parameters using recent methods and models. The estimation of wind-driven waves on small water reservoirs and their effects on water reservoir structures rarely are applied, although it is an important part of the dam height calculation. The analysis of wave run-up on the upstream face of the dam was performed by means of the Slovak Technical Standard (STN), Coastal Engineering Manual (CEM), Shore Protection Manual (SPM) and model designed by American Society of Agricultural and Biological Engineers (ASABE). The estimations of the wave characteristics differ depending on the model; wave height (H13%) within the range 0.32–0.56 m, wave period 1.32–2.11 s and run-up (R2%) 0.84–1.68 m under conditions of design wind speed 25 m·s−1. Results obtained by CEM, SPM models predict lower values than STN and ASABE models. Since the height difference between the dam crest and still water level in the reservoir is only 0.90 m, we can expect overtopping of the crest by waves after the critical wind speed is exceeded.

Feasibility Study of Super-Long Span Bridges Considering Aerostatic Instability by a Two-Stage Geometric Nonlinear Analysis

To meet the need of constructing fixed cross strait links, super-long span bridge with a main span over 2 000[Formula: see text]m is considered as a candidate for their ability to cross deep and wide straits. To this end, some super-long span bridges with proper cable and girder systems were previously proposed and studied. The major design considerations are aimed at adopting new cable material, increasing the entire rigidity of the bridge, stabilizing the dynamic characteristics, strengthening the deck sections, etc. In this paper, a brief review of main cable and girder system is first given of the concepts previously proposed for the design of super-long span bridges. Then some typical examples are studied, focused on various issues related to the design of super-long span bridges, including composite cable, the unstressed length and tension force of the main cable, the stiffness and mass effects of the deck on critical wind speed, and the critical wind speed of various cable systems. The most challenges in super-long span bridges are to solve aerostatic and aerodynamic instability at required design wind speed. In this connection, the wind-induced aerostatic instability of super-long span bridges is studied by a two-stage geometric nonlinear analysis for dead loads and wind loads. The developed program adopted herein for geometric nonlinear analysis was verified and confirmed before. The proposed methods (i.e. composite cable, slotted girder, increasing deck stiffness and mass, cable layout, etc.) obtained for all the examples are in agreement with this study, which indicates applicability of the design approaches presented.

Catchment Based Aerodynamic Performance Analysis of Small Wind Turbine Using a Single Blade Concept for a Low Cost of Energy

For low and medium wind conditions, there is a possibility to harness maximum wind potential reducing the cost of energy by employing catchment-based wind turbine designs. This paper aims to study catchment-based small wind turbine aerodynamic performance for improved efficiency and reduced cost of energy. Hence, design parameters are considered based on specific conditions within a catchment area. The bins and statistical methods implemented with Weibull distribution of wind data for selected sites to characterize the wind conditions and a weighted average method proposed to create representative wind conditions implementing a single blade concept. The blade element method was applied using Matlab code (version R2017a, MathWorks Inc., Natick, MA, US) for aerodynamic design and analysis, and computational fluid dynamics employed using ANSYS—Fluent (version 18.1, ANSYS Inc., Canonsburg, PA, USA) for validation. The performance of the designed blade is evaluated based on annual energy production, capacity factor and power coefficient. Then, for site-specific wind conditions, yearly energy production, and relative cost of energy are examined against rated power. Appropriate rated power for a low cost of energy identified and performance measures evaluated for each site. As a result, a maximum power coefficient of around 51.8% achieved at a design wind speed of 10 m/s, and higher capacity factors of 28% and 50.9% respectively attained for the low and high wind conditions at the proposed rated powers. Therefore, for different wind condition sites, enhanced performance at a low cost of energy could be achieved using a single blade concept at properly selected rated powers employing suitable design conditions and procedures.

New Zealand design wind speeds, directional and lee-zone multipliers proposed for AS/NZS 1170.2:2021

The study aims to estimate design wind speeds and associated directional multipliers, also lee-zone multipliers for New Zealand through the analysis of historical wind data recorded at meteorological stations and also utilising a high-resolution convection-resolving numerical weather prediction model (New Zealand Convective-Scale Model (NZCSM)) analyses. New Zealand’s historical wind data have not been analysed in the past two decades for design wind-load purposes. In addition, no attempt has been made to thoroughly homogenise the mean and gust wind speed data recorded prior to the 1990s and to convert them to equivalent Automatic Weather Stations (AWS) records. Furthermore, lee zones, areas affected by the wind speed-up due to the presence of mountains, can significantly influence the design wind loads, thus, it is crucial to estimate the spatial extent and magnitude of the lee multiplier accurately. In this study, the wind data were initially subjected to a robust homogenisation algorithm and then, they were separated into synoptic and non-synoptic events to gain a better understanding of New Zealand’s gust climatology and sources of extreme events. It was demonstrated that synoptic events dominate the design wind speeds at most locations in New Zealand. For extreme value analysis, three different extreme value distributions were used, namely Type I (using Gumbel, Gringorten and BLUE fitting methods), Type III (using maximum likelihood and probability weighted moments methods), and Peaks-Over-Threshold (POT) approach. In addition, the predictions of NZCSM along with historical wind speeds were used to identify the lee zones, which confirms existing zones and provides evidence to support introducing new zones, and obtain estimates of the lee-multipliers. Substantial changes have been proposed for the next version of the Australian/New Zealand wind-loading standard (AS/NZS 1170.2) based on the results of this study. The changes include adding a new wind region to New Zealand, refinements of wind zone boundaries, revising all regional wind speeds and directional multipliers, and modifying the lee-zone regions and multipliers.

Relationship between wind incidents and wind-induced damage to construction in West Java, Indonesia

In recent decades, the wind has been a major contributor to severe damages to residential constructions in Indonesia. The province of West Java has the highest recorded wind-related damages in the country. Even more, the wind is consistently the second or third source of residential damage, which shows that there is a need to understand the nature of wind as a hazard. However, despite the many cases of destruction due to wind, the data of the destruction is not supported by the wind speed data of the area in question, which makes it difficult to understand how severe the wind condition at the time truly was. Under the classification of the Indonesian National Board for Disaster Management, all cases are classified under severe wind speed or windstorm, even when the wind data is non-existent. This paper explores incidents of wind damages in West Java and matches this data with estimated wind speed conditions obtained from numerical weather model ERA 5. This paper aims to investigate the relationship between wind incidents and wind-induced damage by estimating the wind speed at which wind incidents occur to clarify whether the occurrence is in accordance to the design wind speed, or the strong wind speed definition given by the law. The research was done using field data from the Indonesian National Board for Disaster Management and the West Java Regional Board for Disaster Management. The maximum gust wind speed was estimated from ERA5 reanalysis hourly data. From the analysis of 121 cases between 2011-2018, no gust wind speed that resulted in the damages is above the designated wind speed of 32.1 m/s. Even then, only 2% of the wind speed is above the strong wind definition by the National Board of Disasters at 12.5 m/s. The resulting fragility curve shows that even with a wind speed of 5 m/s and 8 m/s, there is a 50% and 90% possibility of wind-induced damages respectively.

A general-purpose analytical model for reconstructing the thunderstorm outflows of travelling downbursts immersed in ABL flows

A “downburst” is defined as a diverging wind system that occurs when a strong downdraft induces an outflow of damaging winds on or near the ground. Severe wind damage in many parts of the world are often due to thunderstorm outflows and their knowledge is therefore relevant for structural safety and design wind speed evaluation. Nevertheless, there is not yet a shared model for thunderstorm outflows and their actions on structures. In this paper, an analytical model that simulates the horizontal mean wind velocity originated from a travelling downburst is proposed. The horizontal wind velocity is expressed as the vector summation of three independent components: the stationary radial velocity generated by an impinging jet over a flat surface, the downdraft translating velocity, which corresponds to the parent cloud motion, and the boundary layer background wind field at the surface where the downburst is immersed. A parametric analysis is also developed and coupled with the analytical model aiming to investigate two observed downburst events and extract their main parameters – e.g. downdraft diameter, touch-down position, translating downdraft speed and direction, intensity and decay period - in order to reconstruct the space-time evolution of these events and validate the model itself.