• Wind and Structures
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• 제8권4호
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• pp.251-268
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• 2005

This paper describes the work of the International Association for Wind Engineering Working Group E -Dynamic Response, one of the International Codification Working Groups set up at the Tenth International Conference on Wind Engineering in Copenhagen. Comparisons of gust loading factors and wind-induced responses of major codes and standards are first reviewed, and recent new proposals on 3-D gust loading factor techniques are introduced. Then, the combined effects of along-wind, crosswind and torsional wind load components are discussed, as well as the dynamic characteristics of buildings. Finally, the mathematical forms of along-wind velocity spectra for along-wind response calculation and codification of acceleration criteria are discussed.

• Wind and Structures
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• 제22권1호
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• pp.17-41
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• 2016

To address the uncertainty of the flight trajectories caused by the turbulence and gustiness of the wind field over the roof and in the wake of a building, a 3-D probabilistic trajectory model of flat-type wind-borne debris is developed in this study. The core of this methodology is a 6 degree-of-freedom deterministic model, derived from the governing equations of motion of the debris, and a Monte Carlo simulation engine used to account for the uncertainty resulting from vertical and lateral gust wind velocity components. The influence of several parameters, including initial wind speed, time step, gust sampling frequency, number of Monte Carlo simulations, and the extreme gust factor, on the accuracy of the proposed model is examined. For the purpose of validation and calibration, the simulated results from the 3-D probabilistic trajectory model are compared against the available wind tunnel test data. Results show that the maximum relative error between the simulated and wind tunnel test results of the average longitudinal position is about 20%, implying that the probabilistic model provides a reliable and effective means to predict the 3-D flight of the plate-type wind-borne debris.

• Wind and Structures
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• 제24권3호
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• pp.249-265
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• 2017

An efficient and accurate algorithm is proposed to estimate flutter safety factor of suspension bridges satisfying prescribed reliability levels. Uncertainties which arise from the basic wind speed at the bridge deck location, critical flutter velocity, the wind conversion factor from a scaled model to the prototype structure and the gust speed factor are incorporated. The proposed algorithm integrates the concepts of the inverse reliability method and the calculation method of the critical flutter velocity of suspension bridges. The unique feature of the proposed method is that it offers a tool for flutter safety assessment of suspension bridges, when the reliability level is specified as a target to be satisfied by the designer. Accuracy and efficiency of this method with reference to three example suspension bridges is studied and numerical results validate its superiority over conventional deterministic method. Finally, the effects of various parameters on the flutter safety factor of suspension bridges are also investigated.

• 한국방재안전학회논문집
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• 제6권2호
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• pp.1-8
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• 2013

우리나라 전체 재해 60%이상인 태풍과 같은 바람재난으로부터 구조물이나 외장재가 안전과 사용성 측면에서 설계되려면 내풍설계과정에서 기본풍속, 설계속도압, 풍하중 등 많은 파라미터들이 요구된다. 본 논문에서는 최근 2003년부터 2012년까지의 10년 동안 년최대풍속이 발생한 날의 풍속으로부터 확률과정과 확률분포, 통계적 성질 등을 알아보기 위하여 8개의 대표지점을 여수, 인천, 서울, 청주, 원주, 대구, 속초, 울릉도로 선정했다. 선정된 각 지점에 대한 최근 10년 동안의 풍속자료는 기상청으로부터 획득했다. 각 지점의 획득한 풍속자료는 우리나라를 직접 통과하면서 영향을 미친 태풍과 통과는 안했지만 간접 영향을 미친 태풍, 년최대순간풍속과 년최대평균퐁속이 같은 날 등을 고려 90개의 앙상블 중 선별된 33개의 모집단에 대한 풍속자료의 확률과정 및 확률분포의 특성을 비교 검토하였다.

• Wind and Structures
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• 제1권4호
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• pp.287-302
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• 1998

This paper formulates a probabilistic model which is able to represent the maximum instantaneous wind velocity. Unlike the classical methods, where the randomness is circumscribed within the mean maximum component, this model relies also on the randomness of the maximum value of the turbulent fluctuation. The application of the FOSM method furnishes the first and second statistical moments in closed form. The comparison between the results herein obtained and those supplied by classical methods points out the central role of the turbulence intensity. Its importance is exalted when extending the analysis from the wind velocity to the wind pressure.

• Wind and Structures
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• 제15권1호
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• pp.1-15
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• 2012

High-resolution wind data were acquired from a 100-m high offshore tower during the passage of Typhoon Hagupit in September, 2008. The meteorological tower was equipped with an ultrasonic anemometer and a number of cup anemometers at heights between 10 and 100 m. Wind characteristics of the strong typhoon, such as mean wind speed and wind direction, turbulence intensity, turbulence integral length scale, gust factor and power spectra of wind velocity, vertical profiles of mean wind speed were investigated in detail based on the wind data recorded during the strong typhoon. The measured results revealed that the wind characteristics in different stages during the typhoon varied remarkably. Through comparison with non-typhoon wind measurements, the phenomena of enhanced levels of turbulence intensity, gust factors, turbulence integral length scale and spectral magnitudes in typhoon boundary layer were observed. The monitored data and analysis results are expected to be useful for the wind-resistant design of offshore structures and buildings on seashores in typhoon-prone regions.

• Wind and Structures
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• 제35권6호
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• pp.419-430
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• 2022

In wind-resistant designs, wind velocity is assumed to be a Gaussian process; however, local complex topography may result in strong non-Gaussian wind features. This study investigates the non-Gaussian wind features over complex terrain under atmospheric turbulent boundary layers by the large eddy simulation (LES) model, and the turbulent inlet of LES is generated by the consistent discretizing random flow generation (CDRFG) method. The performance of LES is validated by two different complex terrains in Changsha and Mianyang, China, and the results are compared with wind tunnel tests and onsite measurements, respectively. Furthermore, the non-Gaussian parameters, such as skewness, kurtosis, probability curves, and gust factors, are analyzed in-depth. The results show that the LES method is in good agreement with both mean and turbulent wind fields from wind tunnel tests and onsite measurements. Wind fields in complex terrain mostly exhibit a left-skewed Gaussian process, and it changes from a softening Gaussian process to a hardening Gaussian process as the height increases. A reduction in the gust factors of about 2.0%-15.0% can be found by taking into account the non-Gaussian features, except for a 4.4% increase near the ground in steep terrain. This study can provide a reference for the assessment of extreme wind loads on structures in complex terrain.

• Structural Engineering and Mechanics
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• 제72권5호
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• pp.541-555
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• 2019

Wind induced dynamic responses on hyperbolic cooling tower (HCT) shells are complicated functions of structure and wind properties, such as the fundamental frequency f_min, damping ratio ζ, wind velocity V, correlationship in meridian direction and so on, but comprehensions on the sensitivities of the dynamic responses to these four factors are still limited and disagree from each other. Following the dynamic calculation in time domain, features of dynamic effects were elaborated, focusing on the background and resonant components σ_B and σ_R, and their contributions to the total rms value σ_T. The σ_R is always less than σ_B when only the maximum σ_T along latitude is concerned and the contribution of σ_R to σ_T varies with responses and locations, but the σ_R couldn't be neglected for structural design. Then, parameters of the above four factors were artificially adjusted respectively and their influences on the gust responses were illustrated. The relationships of σ_R and the former three factors were expressed by fitted equations which shows certain differences from the existing equations. Moreover, a new strategy for wind tunnel tests aiming at surface pressures and the following dynamic calculations, which demands less experiment equipment, was proposed according to the influence from meridian correlationship.

• Wind and Structures
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• 제20권3호
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• pp.469-488
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• 2015

A full-scale instrumented low-rise building with gable roof was built at a coastal site with a high incidence of tropical cyclones for monitoring of wind effects on the building during windstorms. This paper presents the field measurements of the wind velocity field around and the wind-induced pressures on the low-rise building during the passage of severe tropical storm Soudelor. Near-ground wind characteristics such as wind speed, wind direction, turbulence intensity, gust factor, turbulence integral length scale and wind velocity spectra were investigated. The wind-induced pressures on the roof of the building were analyzed and discussed. The results revealed that the eave and ridge edges on the roof were subjected to the most severe suction pressures under quartering winds. These suction pressures showed obvious non-Gaussian behavior. The measured results were compared with the provisions of ASCE 7-10 to assess the suitability of the code of practice for the wind-resistant design of low-rise buildings under tropical cyclones. The field study aims to provide useful information that can enhance our understanding of the extreme wind effects on low-rise buildings in an effort to reduce tropical cyclone wind damages to residential buildings.

• Wind and Structures
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• 제21권2호
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• pp.241-272
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• 2015

In the current study, dynamic and quasi-static analyses were performed to investigate the response of multiple-spanned and single-spanned transmission line conductors under both downburst and synoptic winds considering different wind velocities and different length spans. Two critical downburst configurations, recommended in the literature and expected to cause maximum conductor reactions, were considered in the analyses. The objective of the study was to assess the importance of including the dynamic effect when predicting the conductor's reactions on the towers. This was achieved by calculating the mean, the background and the resonant reaction components, and evaluating the contribution of the resonant component to the peak reaction. The results show that the maximum contribution of the resonant component is generally low (in the order of 6%) for the multiple-spanned system at different wind velocities for both downburst and synoptic winds. For the single-spanned system, the result show a relatively high maximum contribution (in the order of 16%) at low wind velocity and a low maximum contribution (in the order of 6%) at high wind velocity for both downburst and synoptic winds. Such contributions may justify the usage of the quasi-static approach for analyzing transmission line conductors subjected to the high wind velocities typically used for the line design.