Design Wind Speed Research Articles

A Generalized Framework for Risk-Based Extreme Load Analysis in Offshore System Design

Abstract The primary aim of this research is to consider the correlation among environmental factors in calculating 100 and 1000 years of extreme load design criteria. This is done by considering load as energy transferred from external environment to the offshore system. Also, incorporating spatial and temporal dependence of environmental variables in the context of offshore design. A bivariate extreme value distribution and a conditional joint return level function are developed using the Gumbel–Hougaard copula. The offshore design risk criteria are developed for the finer grid locations (0.1 deg × 0.1 deg latitude/longitude grid) considering joint extreme wind and wave energy. The developed approach is tested using data for the Flemish Pass basin off the east coast of Canada. Along with the primary aim, the impact of climate change is investigated (time and space variability) by implementing the proposed methodology in two cases: the periods from 1959 to 1988 and 1989 to 2018. This study observed that climate change has caused 30% less correlation between wind speed and wave height in recent years (1989–2018) compared to the period of 1959–1988. The proposed extreme design wind speed is 39.7 m/s, and significant wave height is 16.4 m; their joint exceeding probability is 5.80 × 10−5 over an annual basis for a scenario of 100-year.

Reliability assessment of guyed transmission towers through active learning metamodeling and progressive collapse simulation

This manuscript presents a novel approach to the reliability of guyed transmission line towers (TLTs) considering complete geometric and material non-linear analyses, bolt slippage effects, and progressive collapse simulation, using active learning Kriging to handle the computational burden. In the existing literature, such issues have been considered separately, with the main focus on self-supporting towers. Herein, novelty arises from the combined consideration of the above and the addressing of guyed TLTs. Yet, because the wind speed variability is much higher than those related to the mechanical model, a modified initial sampling plan strategy is successfully proposed to reduce the computational time required. The application case-study addressing long transmission lines in midwest Brazil is also relevant, considering the recent updating of design wind speeds, with increases of up to 25%. Failure probabilities obtained using code resistance models indicate the need for tower retrofitting. However, the more accurate assessment via collapse simulation shows that the support is still safe, even for the updated wind speeds. Results demonstrate the accuracy and efficiency of the proposed analysis framework and show the importance of using accurate numerical models in retrofit evaluations.

Reliability of a structure stricken by a tornado

A tornado may become a very dangerous climatic action for any structure, depending on the tornado intensity and extent of the structure. The origin of a tornado, its range and further activity appear to be unpredictable and completely random. The strike of a tornado to a structure depends on the tornado movement and the structure extent. The tornado intensity is specified by the wind speed, following observed damages and consequences. The probability of a tornado strike on a structure depends on the extent of the structure itself, on the tornado range, and the extent of the considered reference area, for which data concerning tornado appearance are available. The probability of failure of a structure is given by the product of the probability of contact of a tornado with the structure and the probability of exceeding the design speed of the tornado wind. The probability of exceeding the design wind speed depends on the assumed distribution of wind speed and the frequency of tornadoes during the required lifetime of the structure. The target failure probability of common structures presented in available documents is 10−6 per year, and 10−7 per year of structures in power plants. However, it is not clear how these criteria have been derived. Further development of reliability theory of tornado-stricken structures is recommended to be focused on the risk analysis of appropriate systems, of which the considered structures are elements, on the target failure probability, on detailed analysis of the probability distribution of tornado wind speed and their frequency during the required lifetime of the structures.

Application of metaheuristic optimization algorithms to evaluate the geometric and kinematic parameters of downbursts

Strong localized downbursts generated in thunderstorms can produce surface winds very dangerous for civil structures and infrastructures. Modelling and simulating such severe wind systems is therefore extremely important for structural safety and design wind speed evaluation. This paper deals with the downburst wind field simulation by means of an optimization algorithm that uses a downburst analytical model, previously developed by the authors, and two metaheuristic algorithms, namely the Differential Evolution (DE) and the Teaching-Learning-Based Optimization (TLBO), for the downburst kinematic and geometrical parameters evaluation. The optimization problem minimizes the relative error between recorded and simulated wind speed and direction time histories. A comparison is made between the performance of two algorithms for ten thunderstorm events measured in north-western Italy between October 2011 and October 2015. Both algorithms provide solutions which are coherent with the downburst parameters values present in literature. TLBO outperforms DE since it has a faster convergence rate to the optimal solution.

Risk assessment of rehabilitation strategies for steel lattice telecommunication towers of Greece under extreme wind hazard

The risk and losses associated with the wind-induced failure of existing steel lattice telecommunication towers are assessed for a number of upgrade/replace/redesign schemes. Specifically, a performance-based wind engineering framework is employed for assessing a typical tower topology used by EU telecommunication network operators over four different cases: a conventional design, its corroded version after 60 years, a strengthened version of the corroded tower by applying fibre-reinforced polymer plates, and a redesign with high-strength steel. Multiple potential sites of installation were considered throughout coastal and mainland Greece, comprising two different groups of design wind speed. Mischaracterization of the site-specific wind distribution is by far the most important risk factor, with corrosion coming right behind. Still, selecting a rehabilitation approach does not depend only on site and tower characteristics, but also on the projected direct and indirect losses. By considering service to different populations, even after 60 years of corrosion, the “Do Nothing” approach may still be competitive when serving few residents and for short projected lifetime, while an upgrade is considered optimal for larger towns, or wherever higher revenue is on the line.

Using historical tropical cyclone climate datasets to examine wind speed recurrence for coastal Australia

Likelihood estimates of extreme winds, including those from tropical cyclones (TCs) at certain locations are used to inform wind load standards for structural design. Here, wind speed average recurrence intervals (ARIs) determined from TC climate data dating back to the 1970s in two quantile–quantile adjusted reanalysis datasets (ERA5 and BARRA [1990]), and best-track observations for context, were compared with Standardized ARIs (AS/NZS) across seven tropical and two subtropical Australian inland coastal regions. The novelty of this work lies in determining TC-wind speed ARIs from a range of datasets that are not typically used to evaluate this metric. Inherent differences between the data used to determine the Standard ARIs (large sample size allow for larger extrapolations; GEV function) and TC data ARIs (smaller sample size and less certain data; the more asymptotic Lognormal/Weibull functions are used) led to the use of different extreme value functions. Results indicated that although these are two distinct ways of determining design wind speeds, when they are considered equivalent, there was a moderate reproduction of the ARI curves with respect to the Standard in both reanalysis datasets, suggesting that similar analyses using climate model products can provide useful information on these types of metrics with some caveats. Trends in TC wind strength affecting coastal Australia were also analyzed, indicating a potential slight downtrend in tropical West coast TC wind strength and slight uptrend for tropical East coast TC wind strength, noting considerable uncertainty given the short time period and limitations of data quality including over longer time periods. Such trends are not only limited to the relationship between TC intensity and anthropogenic warming, but also to regional changes in TC frequency and track direction. This could lead to significant trends emerging in regional Australian TC wind gust strength before several decades of warming have occurred. It is hoped that climate models can provide both longer-term and a more homogenous base for these types of evaluations and subsequent projections with respect to climate change simulations.

Correction of historical records to improve the reliability of design wind speeds

It is not uncommon that design wind speeds are derived from measured data for which the sampling period is longer than the averaging time, e.g. 10-min averages measured once every hour; we call these downsampled data. Using downsampled data has the effect of shifting the calibrated distribution of the yearly maxima to the left, thus reducing the predicted return wind speed. The origin of this has probably to be found in the fact that a large amount of research on the assessment of design wind speeds was developed in the UK, where hourly wind speed averages were available, measured twenty-four times a day, i.e. contiguously. Procedures were then applied also in the case in which downsampled data were available, apparently disregarding the bias this brings. Indeed, even contiguous measurement of mean wind speeds is insufficient, as for the proper evaluation of the return wind speed continuous measurements would be needed. In this paper, the difference between continuous, contiguous disjunct and downsampled disjunct data measurements is pointed out, and the effects of downsampling on the statistics of the extreme wind speed are quantified. A technique for correction of disjunct measurements is proposed and validated in order to remove the bias deriving from downsampling and to improve the reliability of design wind speeds and velocity pressures. Finally, the procedure is applied to datasets from four Italian meteorological stations showing an increase of the return velocity pressure after correction of about 10% to 30%.

Study on the effect of inflow conditions on wind flow acceleration in mountainous micro-topography

The acceleration of wind flow in mountainous areas can cause the destruction or collapse of transmission towers. The wind speed and direction of inflow have a significant impact on the flow acceleration in mountainous areas. The mountain terrain in the coastal area of Fujian was selected to study the influence of the inflow wind speed and direction on the acceleration effect. By analyzing the radar chart of the wind speed acceleration ratio of the monitoring points under 24 wind direction angles, the variation law of the wind speed acceleration ratio is consistent with the trend of the influence law obtained by the analysis of the surrounding terrain. The obtained simulation results are correct and credible, which can be used to correct the design wind speed of transmission lines in mountainous areas.

Structural Behavior of a Composite Curtain Wall Fabricated by the Fused Deposition Modeling 3D Printing Method.

In this era of the fourth industrial revolution, the integration of big data and 3D printing technology with the construction industry has maximized productivity. Currently, there is an active effort to research the optimal cladding structure through 3D printing technology to reduce production costs. This paper proposes a new type of 3D print curtain wall, using a high-strength ABS-M30 polymer panel, which is stronger than the standard acrylonitrile butadiene styrene (ABS) polymer, as an internally reinforced structure. This structure is fabricated via fused deposition modeling, a 3D printing method, to reduce the weight of the general cement panel. In addition, the shape of the polymer board was designed; three shapes were considered—O, W, and X types—which aided in further reducing the weight of the cladding. After comparing the center deformation of the structure through a lateral load test and finite element method analysis, the optimal model was selected. The measured data of the two methods at a design wind speed of 100% showed a difference of approximately 10%; however, at 150% of the design wind speed, the difference between the two sets of data increased to 27%.

Design Wind Speed for Buildings and Facilities With Non-Standard Design Life in Canadian Wind Climates

The design life can be longer than 50 years for critical structures or infrastructures and shorter than 50 years for non-residential structures or construction periods. Some building codes provide methods to derive factors for adjusting the design wind speeds for construction periods. Eurocode 1 provides a probability factor for calculating the design wind speeds for a specific return period regulated for a construction period of less than 1 year. The Australian ABCB Temporary Structures standard provides design wind speed for construction using a different assumption. The ASCE 37 in the USA provides design wind speed reduction factors for a design life less than 5 years by maintaining the probability of exceedance of the factored wind load for 50-year design life the same for a shorter design life. These approaches can result in different results and deserve some comparisons. The present study included another method that maintains the structural reliability of the non-standard design life the same as the structural reliability for the design life of 50 years. The derived factors for a design life shorter than 50 years using these methods were compared considering the Canadian wind climates. The calculated design wind speed adjustment factors for design life longer than 50 years were evaluated using various techniques and compared with the commonly used importance factors. The present study also characterized the directionality and seasonality of the Canadian wind climates.

A Bayesian approach for site-specific extreme load prediction of large scale bridges

To measure uncertainties of site-specific extreme loads for a signature bridge, a probabilistic method is developed based on structural health monitoring data in the Bayesian context. Compared with respective design loads, the probability of the predicted extreme load exceeding the design one is used to determine whether the design load is sufficient. The generalized Pareto distribution was first employed to model extreme value information. Then, Bayesian estimation was applied to predict probabilistic distributions of extreme loads, accounting for uncertainties within the prediction process. Finally, the effectiveness of the proposed method was validated through wind speed and temperature measurements from the Nanjing Dashengguan Yangtze River Bridge. The extreme wind speed and four types of thermal loads were predicted based on site-specific monitored loading data by using Bayesian estimation of the generalized Pareto distribution. As a result, the design wind speed and design change in uniform temperature are sufficient for the signature bridge. However, the probability that the predicted extreme vertical girder temperature difference exceeds the design one is 99.96%, and the probabilities subject to the transverse girder temperature difference and tower temperature difference are almost 100%.

Site or regional design wind speeds?

Estimates of high return period design wind speeds are required to achieve an acceptable probability of failure. These can be found by fitting an appropriate distribution to observed data but is complicated by spatial variation of the wind climate, therefore it is unclear which data are relevant at a particular location. We aim to frame this problem in terms of model selection and the bias variance trade-off. Existing models for incorporating site versus regionally averaged statistics are expressed in terms of key parameters, which allow the errors associated with each model to be derived. It is found that using a characteristic wind speed in codification combines the site statistics (low bias) with regionally averaged statistics (low variance). The return period of the characteristic wind speed is shown to act as a parameter controlling the relative weighting of these models. This insight is used to develop an optimal (minimum mean square error) estimator of the design wind speed, which is shown to vary based on both the available quantity of data at a particular site and how well this data corresponds to the regional average. Some practical advantages of this optimal model are then demonstrated at several South African stations.

Integrating storm surge modeling with traffic data analysis to evaluate the effectiveness of hurricane evacuation

An integrated storm surge modeling and traffic analysis were conducted in this study to assess the effectiveness of hurricane evacuations through a case study of Hurricane Irma. The Category 5 hurricane in 2017 caused a record evacuation with an estimated 6.8 million people relocating statewide in Florida. The Advanced Circulation (ADCIRC) model was applied to simulate storm tides during the hurricane event. Model validations indicated that simulated pressures, winds, and storm surge compared well with observations. Model simulated storm tides and winds were used to estimate the area affected by Hurricane Irma. Results showed that the storm surge and strong wind mainly affected coastal counties in south-west Florida. Only moderate storm tides (maximum about 2.5 m) and maximum wind speed about 115 mph were shown in both model simulations and Federal Emergency Management Agency (FEMA) post-hurricane assessment near the area of hurricane landfall. Storm surges did not rise to the 100-year flood elevation level. The maximum wind was much below the design wind speed of 150–170 mph (Category 5) as defined in Florida Building Code (FBC) for south Florida coastal areas. Compared with the total population of about 2.25 million in the six coastal counties affected by storm surge and Category 1–3 wind, the statewide evacuation of approximately 6.8 million people was found to be an over-evacuation due mainly to the uncertainty of hurricane path, which shifted from south-east to south-west Florida. The uncertainty of hurricane tracks made it difficult to predict the appropriate storm surge inundation zone for evacuation. Traffic data were used to analyze the evacuation traffic patterns. In south-east Florida, evacuation traffic started 4 days before the hurricane’s arrival. However, the hurricane path shifted and eventually landed in south-west Florida, which caused a high level of evacuation traffic in south-west Florida. Over-evacuation caused Evacuation Traffic Index (ETI) to increase to 200% above normal conditions in some sections of highways, which reduced the effectiveness of evacuation. Results from this study show that evacuation efficiency can be improved in the future by more accurate hurricane forecasting, better public awareness of real-time storm surge and wind as well as integrated storm surge and evacuation modeling for quick response to the uncertainty of hurricane forecasting.

Characteristics of wind loads on Twin-Tower structure in comparison with single tower

To provide a general guidance for the wind-resistant design of super-tall twin towers, a study was conducted to investigate the aerodynamic and structural dynamic characteristics of twin towers in comparison with the isolated single tower. It was found that the mutual aerodynamic interference between two towers may have a beneficial effect of disrupting the regular shedding of vortices and causing the across-wind oscillation of the twin towers appreciably smaller than that of the single tower. This beneficial effect is a function of the relative spacing between two towers and the wind direction. When the twin towers are side-by-side to wind, the beneficial effect is apparent if the relative spacing is about 1.0 or less, but it becomes negligible when the relative spacing reaches 2.0. When the twin towers are in tandem configuration to wind, the beneficial effect will remain valid until the maximum tested relative spacing of 2.0. It is also found that wind forces applied to the twin towers may contain a large proportion of out-of-phase components, which act on the two towers in opposite directions, and the corresponding structural response can be well controlled by structural links between the two towers. Therefore, the role and effectiveness of structural links in controlling wind-induced structural responses can be evaluated by the percentage of the out-of-phase components over the total wind forces, which is again a function of the relative spacing, design wind speed, wind direction of concern, and reduced building frequencies. A case study of the 570 m super-tall twin towers verified the conclusions drawn from the general study, and the use of structural links was proved to be able to reduce the design wind loads and building accelerations by more than 20%.

Revisiting Basic Wind Speed of Metro Cities of India

AbstractAn accurate prediction of design wind speed is critical to the estimation of wind loads on any earth-bound civil engineering structure. Concerns have been raised within the Indian design co...

A Nonstationary Wind Speed Frequency Model over South Korea: In the Context of Bayesian Mixture Distribution Model

Kim, H.-J.; Kim, Y.-T.; Kim, T.-W., and Kwon, H.-H., 2021. A nonstationary wind speed frequency model over South Korea: In the context of Bayesian mixture distribution model. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 196–200. Coconut Creek (Florida), ISSN 0749-0208. It has been well recognized that extreme wind speed processes often feature nonstationary behavior, which may not be effectively modeled within a stationary frequency modeling framework. Furthermore, univariate Gumbel distribution has been commonly used for wind speed frequency analysis in Korea. However, the distributional changes in extreme wind speed have been globally observed, including Korea. More specifically, the univariate Gumbel distribution based wind speed frequency analysis often failed to describe multimodal behaviors which are mainly influenced by distinct climate conditions. In this perspective, this study explores a mixture distribution based nonstationary frequency (MDNF) model in a changing climate within a Bayesian framework. It was found that the MDNF model can effectively account for the time-varying moments (i.e., mean and variance) in a two-component mixture distribution. The MDNF model showed more robust results for describing the upper tail of the distribution, which plays a crucial role in estimating the design wind speed.

Typhoon wind hazard estimation by full-track simulation with various wind intensity models

A general framework of typhoon full-track simulation for the Western North Pacific (WNP) basin is presented in this paper. Specifically, an empirical TC track model integrated with two intensity models, i.e., a classical Vickery intensity regression model (VIRM) and a novel Markov Environment-Dependent Hurricane Intensity Model (MeHiM) are developed. The applicability of MeHiM for typhoon simulation in WNP basin is validated by comparing several metrics (i.e., intensity spatial distribution, probabilistic distributions) with those from observation data. The full-track model parameters are calibrated and modified for the local area of the WNP basin, and storm tracks from the genesis to lysis are generated. The proposed full-track typhoon simulation framework together with a widely-used wind field model is employed to estimate design wind speed with a given return period for ten major cities of Southeast China. The results show that the estimated 100-year return period design wind speeds in simulated tropical cyclone climates are in good agreement with that prescribed in the current design code for some cities. For other cities, the comparison is complicated.

Wind-induced fatigue analysis of Yueyang Dongting Lake Suspension Bridge

Recent demand for a longer span has complicated the dynamic behaviours in the strong wind. The limited amplitude but frequent occurred buffeting response of bridge affect fatigue resistance of the bridge, which should be considered. The time-domain buffeting response and fatigue performance of Yue yang Dongting Lake Suspension Bridge are realized by mixed programming with MATLAB and ANSYS. The gusty wind was simulated by the WAWS method, while the self-excited force was modelled as the elemental aeroelastic stiffness and damp matrices by the element Matrix 27. The mode superposition method was then adapted to calculate the buffeting response of the bridge in ANSYS, and its accuracy is verified by the results of the RMS and PSD using the traditional frequency-domain method. It was found that the fatigue life reliability of the suspender neat tower of the leeward side is 97.54% during the structure's service in the design wind speed.

Investigation of the Scruton Number Effects of Wind-Induced Unsteady Galloping Responses of Bridge Suspenders

When the critical wind speed of vortex-induced resonance is close to that of quasi-steady galloping, a type of coupled wind-induced vibration that is different from divergent galloping can easily occur in a rectangular bar. It is a type of “unsteady galloping” phenomenon wherein the response amplitude increases linearly with the increase in the wind speed, while a limit cycle oscillation is observed at each wind speed, whose mechanism is still in research. Mass and damping are the key parameters that affect the coupling degree and amplitude response estimation. For a set of rectangular section member models with a width-to-height ratio of 1.2, by adjusting the equivalent stiffness, equivalent mass, and damping ratio of the model system and performing comparative tests on the wind-induced vibration response of the same mass with different damping ratios, it is possible to achieve the same damping ratio with different masses and the same Scruton number with different masses and damping combinations under the same Reynolds number. The results show that the influence of the mass and damping parameters on the “unsteady galloping” amplitude response is independent, and the weight is the same in the coupling state. The Scruton number “locked interval” (12.4–30.6) can be found in the “unsteady galloping” amplitude response, and the linear slope of the dimensionless wind speed amplitude response curve does not change with the Scruton number in the “locked interval.” In addition, a “transition interval” (26.8–30.6) coexists with the “locked interval” wherein the coupling state of the wind-induced vibration is converted into the uncoupled state. The empirical formula for estimating the “unsteady galloping” response amplitude is modified and can be used to predict the amplitude within the design wind speed range of similar engineering members.

Cyclone wind hazard assessments for eastern coastal cities in India using a fast-predictive model

Tropical cyclone wind-induced hazards for the eastern coastal built environments of India can be severe. The extreme cyclone winds can cause damage to structures and infrastructures and losses of lives and economies. The current building code of India provides design wind speeds for the eastern coastal cyclone-prone regions. These design wind speeds were determined without considering extreme wind speeds associated with different weather types, such as thunderstorms or cyclones. The cyclone simulation technique has not been considered to update the design wind speeds for India's eastern coastal cyclone-prone regions. Several previous studies used the regional maximum sustained wind speeds to derive the design level cyclone-induced wind speeds. This approach differs from advanced cyclone simulation techniques and provides overly conservatism. The effect of using the regional maximum sustained wind speeds of cyclones in estimating the design wind speeds was investigated quantitatively in this study. A fast-predictive cyclone wind hazard model was proposed to assess the cyclone wind hazards. This model used simple wind field modeling and directly applied the historical best track datasets. The performance of this model was validated by comparing the predicted design level tropical cyclone wind speeds for selected coastal cities in the USA and China to those provided by the local building code or reported in previous studies using advanced tropical cyclone simulation models. This fast-predictive model was used to calculate the peak cyclone wind speeds and predict the 50-year return period cyclone wind speeds for twenty eastern coastal cities in India. The predicted 50-year return period cyclone wind speeds using the fast-predictive model were compared with those predicted using the regional maximum sustained wind speeds and current code design wind speeds.