• Title, Summary, Keyword: wind-induced response characteristics

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Wind-induced vibration characteristics and parametric analysis of large hyperbolic cooling towers with different feature sizes

  • Ke, Shitang;Ge, Yaojun;Zhao, Lin;Tamura, Yukio
    • 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.

Effects of taper and set-back on wind force and wind-induced response of tall buildings

  • Kim, Yongchul;Kanda, Jun
    • Wind and Structures
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    • v.13 no.6
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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.

Characteristics of wind loading on internal surface and its effect on wind-induced responses of a super-large natural-draught cooling tower

  • Zou, Yun-feng;Fu, Zheng-yi;He, Xu-hui;Jing, Hai-quan;Li, Ling-yao;Niu, Hua-wei;Chen, Zheng-qing
    • Wind and Structures
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    • v.29 no.4
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    • pp.235-246
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    • 2019
  • Wind loading is one of important loadings that should be considered in the design of large hyperbolic natural-draught cooling towers. Both external and internal surfaces of cooling tower are under the action of wind loading for cooling circulating water. In the previous studies, the wind loads on the external surface attracted concernedly attention, while the study on the internal surface was relatively ware. In the present study, the wind pressure on the internal surface of a 220 m high cooling tower is measured through wind tunnel testing, and the effect of ventilation rate of the packing layer on internal pressure is a major concern. The characteristics of internal wind pressure distribution and its effect on wind-induced responses calculated by finite element method are investigated. The results indicate that the wind loading on internal surface of the cooling tower behaves remarkable three-dimensional effect, and the pressure coefficient varies along both of height and circumferential directions. The non-uniformity is particularly strong during the construction stage. Analysis results of the effect of internal pressure on wind-induced responses show that the size and distribution characteristics of internal pressure will have some influence on wind-induced response, however, the outer pressure plays a dominant role in the wind-induced response of cooling tower, and the contribution of internal pressure to the response is small.

An Analysis of the Contribution Pattern of Vortex-Induced Load Components to Across-Wind Response (와류하중 구성성분에 따른 풍직각방향 진동 기여 특성 분석)

  • Hwang, Jae-Seung
    • Journal of the Architectural Institute of Korea
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    • v.36 no.7
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    • pp.147-154
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    • 2020
  • As the vortices around the structure are transferred to the dynamic wind load, across-wind vibration is induced, and the magnitude of the vibration is larger than the along-wind vibration when the height of the structure is increased. In this study, in order to quantitatively evaluate across-wind response, the vortex-induced load components are classified according to their own original source, and the effect of each component on the vibration is analyzed. The load is identified from the response of the structure by inverse problem, and these load components are obtained by Kalman filtering based on the state equation realized from the distribution characteristics of loads spectrum in the frequency domain. The proposed load decomposition process for vortex-induced load components is verified by performing an aero-elastic model test for the circular cylinder model in the atmospheric boundary layer wind tunnel, and the pattern in which each load component contributes to the across-wind response is analyzed, and finally the original source of the loads as well as the unique behavior of across-wind response can be precisely understood.

Design of an actuator for simulating wind-induced response of a building structure

  • Park, Eun Churn;Lee, Sang-Hyun;Min, Kyung-Won;Chung, Lan;Lee, Sung-Kyung;Cho, Seung-Ho;Yu, Eunjong;Kang, Kyung-Soo
    • Smart Structures and Systems
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    • v.4 no.1
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    • pp.85-98
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    • 2008
  • In this paper, excitation systems using a linear mass shaker (LMS) and an active tuned mass damper (ATMD) are presented to simulate the wind induced responses of a building structure. The actuator force for the excitation systems is calculated by using the inverse transfer function of a target structural response to the actuator. Filter and envelop functions are used to prevent the actuator from exciting unexpected modal responses and an initial transient response and thus, to minimize the error between the wind and actuator induced responses. The analyses results from a 76-story benchmark building problem for which the wind load obtained by a wind tunnel test is given, indicate that the excitation system installed at a specific floor can approximately reproduce the structural responses induced by the wind load applied to each floor of the structure. The excitation system designed by the proposed method can be effectively used for evaluating the wind response characteristics of a practical building structure and for obtaining an accurate analytical model of the building under wind load.

Aspects of the dynamic wind-induced response of structures and codification

  • Tamura, Yukio;Kareem, Ahsan;Solari, Giovanni;Kwok, Kenny C.S.;Holmes, John D.;Melbourne, William H.
    • Wind and Structures
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    • v.8 no.4
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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.

Effects of coupled translational-torsional motion and eccentricity between centre of mass and centre of stiffness on wind-excited tall buildings

  • Thepmongkorn, S.;Kwok, K.C.S.
    • Wind and Structures
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    • v.5 no.1
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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.

Dynamic characteristics and wind-induced vibration coefficients of purlin-sheet roofs

  • Zhang, Yingying;Song, Xiaoguang;Zhang, Qilin
    • 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.

Design of a Linear Mass Excitation System for Simulating Wind-induced Responses of a Building Structure (풍하중 구현 및 내풍특성 평가를 위한 선형질량 가진시스템 설계)

  • Park, Eun-Churn;Lee, Sang-Hyun;Min, Kyung-Won;Kang, Kyung-Soo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.661-668
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    • 2007
  • In this paper, excitation systems using linear mass shaker (LMS) are presented in order to simulate the wind induced responses of a building structure. The actuator force for the excitation systems is calculated by using the inverse transfer function of a target structural response to the actuator. Filter and envelop function are used such that the error between the wind and actuator induced responses is minimized by preventing the actuator from exciting unexpected modal response and initial transient response. The analyses results from a 76-story benchmark building problem in which wind load obtained by wind tunnel test is given, indicate that the excitation system installed at a specific floor can approximately embody the structural responses induced by the wind load applied to each floor of the structure. The excitation system designed by the proposed method can be effectively used for evaluating the wind response characteristics of a practical building structure and for obtaining an accurate analytical model of the building under wind load.

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Aerodynamic and aero-elastic performances of super-large cooling towers

  • Zhao, Lin;Chen, Xu;Ke, Shitang;Ge, Yaojun
    • Wind and Structures
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    • v.19 no.4
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    • pp.443-465
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    • 2014
  • Hyperbolic thin-shell cooling towers have complicated vibration modes, and are very sensitive to the effects of group towers and wind-induced vibrations. Traditional aero-elastic models of cooling towers are usually designed based on the method of stiffness simulation by continuous medium thin shell materials. However, the method has some shortages in actual engineering applications, so the so-called "equivalent beam-net design method" of aero-elastic models of cooling towers is proposed in the paper and an aero-elastic model with a proportion of 1: 200 based on the method above with integrated pressure measurements and vibration measurements has been designed and carried out in TJ-3 wind tunnel of Tongji university. According to the wind tunnel test, this paper discusses the impacts of self-excited force effect on the surface wind pressure of a large-scale cooling tower and the results show that the impact of self-excited force on the distribution characteristics of average surface wind pressure is very small, but the impact on the form of distribution and numerical value of fluctuating wind pressure is relatively large. Combing with the Complete Quadratic Combination method (hereafter referred to as CQC method), the paper further studies the numerical sizes and distribution characteristics of background components, resonant components, cross-term components and total fluctuating wind-induced vibration responses of some typical nodes which indicate that the resonance response is dominant in the fluctuating wind-induced vibration response and cross-term components are not negligible for wind-induced vibration responses of super-large cooling towers.