• Structural Engineering and Mechanics
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• v.54 no.5
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• pp.891-908
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• 2015

For a systematic study on wind-induced vibration characteristics of large hyperbolic cooling towers with different feature sizes, the pressure measurement tests are finished on the rigid body models of three representative cooling towers with the height of 155 m, 177 m and 215 m respectively. Combining the refined frequency-domain algorithm of wind-induced responses, the wind-induced average response, resonant response, background response, coupling response and wind vibration coefficients of large cooling towers with different feature sizes are obtained. Based on the calculating results, the parametric analysis on wind-induced vibration of cooling towers is carried out, e.g. the feature sizes, damping ratio and the interference effect of surrounding buildings. The discussion shows that the increase of feature sizes makes wind-induced average response and fluctuating response larger correspondingly, and the proportion of resonant response also gradually increased, but it has little effect on the wind vibration coefficient. The increase of damping ratio makes resonant response and the wind vibration coefficient decreases obviously, which brings about no effect on average response and background response. The interference effect of surrounding buildings makes the fluctuating response and wind vibration coefficient increased significantly, furthermore, the increase ranges of resonant response is greater than background response.

• Wind and Structures
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• v.9 no.5
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• pp.345-356
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• 2006

It is well known that cylinder steel stacks are heavily impacted by vortex-induced vibration. However, the wind-induced vibration behaviors of tower-supported steel stacks are not clarified due to a lack of observation. We studied a stack's response to strong winds over a long period of time by observing the extreme wind-induced vibration of a 200 m-high tower-supported steel stack. This experiment aimed to identify the wind-induced vibration properties of a tower-supported steel stack and assess the validity of the vibration control method used in the experiment. Results revealed a trend in wind-induced vibration behavior. In turn, an effective measure for controlling such vibration was defined by means of increasing the structural damping ratio due to the effects of the tuned mass damper to dramatically decrease the vortex-induced vibration of the stack.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2005.04a
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• pp.375-382
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• 2005

In this paper, a practical control method of wind-induced vibration of high-rise buildings is presented in the form of resizing algorithm. In the structural design process for high-rise buildings, the lateral load resisting system for the building is more often determined by serviceability design criteria including wind-induced vibration level. Even though many drift method have been developed in various forms, no practical design method for wind induced vibration has been developed so far. Structural engineers rely upon heuristic or experience in designing wind induced vibration. The performance of the proposed method is evaluated by comparing wind-induced vibration levels estimated both from approximate techniques and wind tunnel test.

• Wind and Structures
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• v.17 no.4
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• pp.399-417
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• 2013

The structural vibration suppression with active constrained layer damping (ACLD) was widely studied recently. However, the literature seldom concerned with the vibration control on flow-induced vibration using active constrained layer. In this paper the wind induced vibration of cantilevered beam is analyzed and suppressed by using random theory together with a velocity feedback control strategy. The piezoelectric material and frequency dependent viscoelastic layer are used to achieve effective active damping in the vibration control. The transverse displacement and velocity in time and frequency domains, as well as the power spectral density and the mean-square value of the transverse displacement and velocity, are formulated under wind pressure at variable control gain. It is observed from the numerical results that the wind induced vibration can be significantly suppressed by using a small outside active voltage on the constrained layer.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.3
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• pp.160-168
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• 2015

Vibration issue of a building structure due to a wind turbine should be resolved for the application of building-augmented wind turbine. In this study, a dynamic analysis for an horizontal-axis upwind wind turbine is carried out to calculate vibration excited to an example building structure. Characteristics of vertical vibration transfer of the building structure are analytically studied and compared with a criteria. Then, a method to isolate the vibration is presented by analyzing the vibration characteristics of the wind turbine, and verified by applying to the building structure.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.43-51
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• 2004

As the slenderness ratio of a high-rise building increases, the lateral load resisting system for the building is more often determined by serviceability design criteria. In serviceability design, the maximum drift and the level of vibration are controlled not to exceed the design criteria. Even though many drift method have been developed in various forms, no practical design method for wind induced vibration has been developed so far. Structural engineers rely upon heuristic or experience in designing wind induced vibration. Development of practical design method for wind induced vibration is required. Generally, wind induced acceleration responses are depending on several variables such as the weight density of a building, damping ratio, the natural period, and etc.. All parameters except the natural period or frequency are usually out of reach for structural engineers, then the wind acceleration response may be proportioned to the natural period. Therefore, in this paper, a wind induced vibration design method based on frequency control technique for high-rise is proposed. The method is applied to vibration design of a 25-story office building for performance evaluation.

• Journal of Korean Association for Spatial Structures
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• v.17 no.1
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• pp.77-84
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• 2017

Vortex-induced vibration and instability vibration of tall buildings are very important fluid-structure interaction phenomenon, and many fundamental questions concerning the influence of body movement on the unsteady aerodynamic force remain unanswered. For tall buildings, there are two experimental methods to investigate the characteristics of unsteady aerodynamic forces, one is forced vibration method and the other is free vibration method. In the present paper, a free vibration method was used to investigate the unsteady aerodynamic force on tall building whose aspect ratio is 9 under boundary layer simulating city area. Wind pressures on surfaces and tip displacements were measured simultaneously, and the characteristics of tip displacements and generalized forces were discussed. It was found that variation of across-wind displacements showed different trend between the case when wind speed increases and wind speed decreases, and the fluctuating generalize forces in across-wind direction of vibrating model are larger than that of static model near the resonant wind speed and approach to the static value. And for higher wind speed range, there were two peaks in across-wind power spectra of generalize forces of vibrating model, which means that two frequency components are predominant in unsteady aerodynamic forces.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.10a
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• pp.124-129
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• 2010

Wind load characteristics is investigated for vibration analysis of wind turbine gearbox. A normal wind model assumed, of which the wind velocity is increased according to the height from ground. A blast wind model is assumed, of which the maximum velocity is located at the center and the velocity profile is normally distributed. The periodical torque and bending moments transmitted to the main shaft of wind turbine are investigated. The average values and the harmonic terms of the transmitted moments are studied on the wind direction of range $-45^{\circ}{\sim}45^{\circ}$ and the bending moment characteristics are examined, which is regarded as the main source of the misalignment of gear train.

• Smart Structures and Systems
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• v.23 no.6
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• pp.683-693
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• 2019

In August 2012, during the passage of the typhoon Haikui (1211), large amplitude vibrations were observed on long hangers of the Xihoumen suspension Bridge, which destroyed a few viscoelastic dampers originally installed to connect a pair of hanger ropes transversely. The purpose of this study is to identify the cause of vibration and to develop countermeasures against vibration. Field measurements have been conducted in order to correlate the wind and vibration characteristics of hangers. Furthermore, a replica aeroelastic model of prototype hangers consisting of four parallel ropes was used to study the aeroelastic behavior of hanger ropes and to examine the effect of the rigid spacers on vibration mitigation. It is shown that the downstream hanger rope experiences the most violent elliptical vibration for certain wind direction, and the vibration is mainly attributed to wake interference of parallel hanger ropes. Based on wind tunnel tests and field validation, it is confirmed that four rigid spacers placed vertically at equal intervals are sufficient to suppress the wake-induced vibrations. Since the deployment of spacers on hangers, server hanger vibrations and clash of hanger ropes are never observed.

• Steel and Composite Structures
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• v.22 no.5
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• pp.1039-1054
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• 2016

This paper presents the dynamic characteristics analysis of the purlin-sheet roofs by the random vibration theories. Results show that the natural vibration frequency of the purlin-sheet roof is low, while the frequencies and mode distributions are very intensive. The random vibration theory should be used for the dynamic characteristics of the roof structures due to complex vibration response. Among the first 20th vibration modes, the first vibration mode is mainly the deformations of purlins, while the rest modes are the overall deformations of the roof. In the following 30th modes, it mainly performs unilateral local deformations of the roof. The frequency distribution of the first 20th modes varies significantly while those of the following 30th modes are relatively sensitive. For different parts, the contributions of vibration modes on the vibration response are different. For the part far from the roof ridge, only considering the first 5th modes can reflect the wind-induced vibration response. For the part near the ridge, at least the first 12 modes should be considered, due to complex vibration response. The wind vibration coefficients of the upwind side are slightly higher than that of the leeward side. Finally, the corresponding wind vibration coefficient for the purlin-sheet roof is proposed.