• Wind and Structures
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• 제10권1호
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• pp.45-60
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• 2007

Transmission tower is a vital component in electrical system. In order to accurately compute the dynamic response and reliability of transmission tower under the excitation of wind loading, a new method termed as probability density evolution method (PDEM) is introduced in the paper. The PDEM had been proved to be of high accuracy and efficiency in most kinds of stochastic structural analysis. Consequently, it is very hopeful for the above needs to apply the PDEM in dynamic response of wind-excited transmission towers. Meanwhile, this paper explores the wind stochastic field from stochastic Fourier spectrum. Based on this new viewpoint, the basic random parameters of the wind stochastic field, the roughness length $z_0$ and the mean wind velocity at 10 m heigh $U_{10}$, as well as their probability density functions, are investigated. A latticed steel transmission tower subject to wind loading is studied in detail. It is shown that not only the statistic quantities of the dynamic response, but also the instantaneous PDF of the response and the time varying reliability can be worked out by the proposed method. The results demonstrate that the PDEM is feasible and efficient in the dynamic response and reliability analysis of wind-excited transmission towers.

• Wind and Structures
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• 제5권6호
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• pp.543-562
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• 2002

The main purpose of this study is to discuss the design wind loads for the structural frames of single-layer latticed domes with long spans. First, wind pressures are measured simultaneously at many points on dome models in a wind tunnel. Then, the dynamic response of several models is analyzed in the time domain, using the pressure data obtained from the wind tunnel experiment. The nodal displacements and the resultant member stresses are computed at each time step. The results indicate that the dome's dynamic response is generally dominated by such vibration modes that contribute to the static response significantly. Furthermore, the dynamic response is found to be almost quasi-static. Then, a series of quasi-static analyses, in which the inertia and damping terms are neglected, is made for a wide range of the dome's geometry. Based on the results, a discussion is made of the design wind load. It is found that a gust effect factor approach can be used for the load estimation. Finally, an empirical formula for the gust effect factor and a simple model of the pressure coefficient distribution are provided.

• Wind and Structures
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• 제37권3호
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• pp.229-243
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• 2023

This study analyzes the response of a tall building with an H-shaped cross-section when subjected to wind loading generated by the same H-shape. As normative standards usually adopt regular geometries for determining the wind loading, this paper shows unpublished results which compares results of the dynamic response of H-shaped buildings with the response of simplified section buildings. Computational Fluid Dynamics (CFD) is employed to determine the steady wind load on the H-shaped building. The CFD models are validated by comparison with wind tunnel test data for the k-ε and k-ω models of turbulence. Transient wind loading is determined using the Synthetic Wind Method. A new methodology is presented that combines Stochastic and CFD methods. In addition, time-history dynamic structural analysis is performed using the HHT method for a period of 60 seconds on finite element models. First, the along-wind response is studied for wind speed variations. The wind speeds of 28, 36, 42, and 50 m/s at 0° case are considered. Subsequently, the dynamic response of the building is studied for wind loads at 0°, 45°, and 90° with a wind speed of 42 m/s, which approximates the point of resonance between gusts of wind and the structure. The response values associated with the first two directions for the H-shaped building are smaller than those for the R-shaped (Equivalent Rectangular Shape) one. However, the displacements of the H-shaped building associated with the latter wind load are larger.

• Wind and Structures
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• 제5권1호
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• pp.61-80
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• 2002

Wind tunnel aeroelastic model tests of the Commonwealth Advisory Aeronautical Research Council (CAARC) standard tall building were conducted using a three-degree-of-freedom base hinged aeroelastic(BHA) model. Experimental investigation into the effects of coupled translational-torsional motion, cross-wind/torsional frequency ratio and eccentricity between centre of mass and centre of stiffness on the wind-induced response characteristics and wind excitation mechanisms was carried out. The wind tunnel test results highlight the significant effects of coupled translational-torsional motion, and eccentricity between centre of mass and centre of stiffness, on both the normalised along-wind and cross-wind acceleration responses for reduced wind velocities ranging from 4 to 20. Coupled translational-torsional motion and eccentricity between centre of mass and centre of stiffness also have significant impacts on the amplitude-dependent effect caused by the vortex resonant process, and the transfer of vibrational energy between the along-wind and cross-wind directions. These resulted in either an increase or decrease of each response component, in particular at reduced wind velocities close to a critical value of 10. In addition, the contribution of vibrational energy from the torsional motion to the cross-wind response of the building model can be greatly amplified by the effect of resonance between the vortex shedding frequency and the torsional natural frequency of the building model.

• 국제초고층학회논문집
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• 제4권1호
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• pp.1-8
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• 2015

A team of researchers and practitioners were recently assembled to prepare a monograph on "Wind-Induced Motion of Tall Buildings: Designing for Habitability". This monograph presents a state-of-the-art report of occupant response to wind-induced building motion and acceptability criteria for wind-excited tall buildings. It provides background information on a range of pertinent subjects, including: ${\bullet}$ Physiological, psychological and behavioural traits of occupant response to wind-induced building motion; ${\bullet}$ A summary of investigations and findings of human response to real and simulated building motions based on field studies and motion simulator experiments; ${\bullet}$ A review of serviceability criteria to assess the acceptability of wind-induced building motion adopted by international and country-based standards organizations; ${\bullet}$ General acceptance guidelines of occupant response to wind-induced building motion based on peak acceleration thresholds; and ${\bullet}$ Mitigation strategies to reduce wind-induced building motion through structural optimization, aerodynamic treatment and vibration dissipation/absorption. This monograph is to be published by the American Society of Civil Engineers (ASCE) and equips building owners and tall building design professionals with a better understanding of the complex nature of occupant response to and acceptability of wind-induced building motion. This paper is a brief summary of the works reported in the monograph.

• Wind and Structures
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• 제19권3호
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• pp.295-320
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• 2014

Starting from an overview on the research on thunderstorms in the last forty years, this paper provides a general discussion on some emerging issues and new frameworks for wind loading on structures in mixed climates. Omitting for sake of simplicity tropical cyclones and tornadoes, three main aspects are pointed out. The first concerns the separation and classification of different intense wind events into extra-tropical depressions, thunderstorms and gust fronts, with the aim of improving the interpretation of the phenomena of engineering interest, the probabilistic analysis of the maximum wind velocity, the determination of the wind-induced response and the safety format for structures. The second deals with the use of the response spectrum technique, not only as a potentially efficient tool for calculating the structural response to thunderstorms, but also as a mean for revisiting the whole wind-excited response in a more general and comprehensive framework. The third involves the statistical analysis of extreme wind velocities in mixed climates, pointing out some shortcomings of the approaches currently used for evaluating wind loading on structures and depicting a new scenario for a more rational scheme aiming to pursue structural safety. The paper is set in the spirit of mostly simplified analyses and mainly qualitative remarks, in order to capture the conceptual aspects of the problems dealt with and put on the table ideas open to discussion and further developments.

• Wind and Structures
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• 제12권2호
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• pp.103-120
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• 2009

Articulated tower platforms due to its compliant nature are more susceptible to the dynamic effects of wind than conventional fixed platforms. Dynamic response analysis of a double hinged articulated tower excited by low frequency wind forces with random waves is presented in this paper. The exposed super structure of the platform, housing the drilling and production facilities is subjected to mean and fluctuating wind loads, while the submerged portion is acted upon by wind driven waves. The fluctuating component of the wind velocity is modeled by Emil Simiu's spectrum, while the sea state is characterized by Pierson-Moskowitz spectrum. Nonlinearities in the system due to drag force, added mass, variable submergence and instantaneous tower orientation are considered in the analysis. To account for these nonlinearities, an implicit time integration scheme (Newmark's-${\beta}$) has been employed which solves the equation of motion in an iterative fashion and response time histories are obtained. The power spectra obtained from random response time histories show the significance of low frequency responses.

• Structural Engineering and Mechanics
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• 제10권6호
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• pp.545-559
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• 2000

A Wind and Structural Health Monitoring System (WASHMS) has been installed in the Tsing Ma suspension Bridge in Hong Kong with one of the objectives being the verification of analytical processes used in wind-resistant design. On 2 August 1997, Typhoon Victor just crossed over the Bridge and the WASHMS timely recorded both wind and structural response. The measurement data are analysed in this paper to obtain the mean wind speed, mean wind direction, mean wind inclination, turbulence intensity, integral scale, gust factor, wind spectrum, and the acceleration response and natural frequency of the Bridge. It is found that some features of wind structure and bridge response are difficult to be considered in the currently used analytical process for predicting buffeting response of long suspension bridges, for the Bridge is surrounded by a complex topography and the wind direction of Typhoon Victor changes during its crossing. It seems to be necessary to improve the prediction model so that a reasonable comparison can be performed between the measurement and prediction for long suspension bridges in typhoon prone regions.

• Wind and Structures
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• 제17권2호
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• pp.227-244
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• 2013

Non-stationary extreme winds such as thunderstorm downbursts are responsible for many structural damages. This research presents a time domain approach for estimating along-wind load effects on tall buildings using multiple wind speed time history samples, which are simulated from evolutionary power spectra density (EPSD) functions of non-stationary wind fluctuations using the method developed by the authors' earlier research. The influence of transient wind loads on various responses including time-varying mean, root-mean-square value and peak factor is also studied. Furthermore, a simplified model is proposed to describe the non-stationary wind fluctuation as a uniformly modulated process with a modulation function following the time-varying mean. Finally, the probabilistic extreme response and peak factor are quantified based on the up-crossing theory of non-stationary process. As compared to the time domain response analysis using limited samples of wind record, usually one sample, the analysis using multiple samples presented in this study will provide more statistical information of responses. The time domain simulation also facilitates consideration of nonlinearities of structural and wind load characteristics over previous frequency domain analysis.

• Wind and Structures
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• 제13권6호
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• pp.499-517
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• 2010

Advances in structural materials and construction methods have resulted in flexible and light tall buildings, making an assessment of structural safety during strong wind and serviceability/habitability during comparable medium/weak wind important design criteria. So far, lots of studies on suppressing the wind-induced responses have been carried out for tall buildings with aerodynamic modification. Most of the studies on aerodynamic modification have forced on the corner modification, while the studies on taper and set-back are limited. Changes of sectional shape through taper and set-back can modify the flow pattern around the models, encouraging more 3-dimensionalities, which results in reducing the wind-induced excitations. This paper discusses the characteristics of overturning moments and wind-induced responses of the tall buildings with height variations. The reduction of mean along-wind and fluctuating across-wind overturning moments are apparent in the suburban area than in urban area. A series of the response analyses, the rms displacement responses of the tall buildings with height variations are reduced greatly, while the rms acceleration responses are not necessarily reduced, showing dependences on wind direction.