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Volume 37, Number 1, July 2023

Due to the irregular shape and the deviation of stiffness center and gravity center, buildings always suffer from complex surface load and vibration response under wind action. This study is dedicated to analyze the surface wind load and wind-induced response of an irregular building, and to discuss the possibility of top swimming pool as a TLD to diminish windinduced vibration of the structure. Wind tunnel test was carried out on a hotel with irregular shape to analyze the wind load and structural response under 8 wind incident angles. Then a precise numerical model was established and calibrated through experimental results. The top swimming pool was designed according to the principle of frequency modulation, and equations of motion of the control system were derived theoretically. Finally, the wind induced response of the structure controlled by the pool was calculated numerically. The results show that both of wind loads and wind-induced responses of the structure are significantly different with wind incident angle varies, and the across-wind response is nonnegligible. The top swimming pool has acceptable damping effect, and can be designed as TLD to mitigate wind response.

Key Words
energy dissipation; irregular buildings; swimming pools; TLD; wind loads

Jianchen Zhao and Hang Jing:School of Civil Engineering, Henan University of Technology, Zhengzhou, Henan, China

Jiayun Xu:Hubei Key Laboratory of Road Bridge & Structure Engineering, Wuhan University of Technology, Wuhan, Hubei, China

The wake behavior of extended flat plate and serration in the trailing edge of S809 airfoil is presented in this experimental study using wind tunnel testing. The clustering of wind turbines in wind parks has recently been a pressing issue, due to the expected increase in power output and deciding the number of wind turbines to be installed. One of the prominent factors which influence the performance of the subsequent wind turbines is the downstream wake characteristics. A series of wind tunnel investigations were performed to assess the downstream near wake characteristics of the S809 airfoil at various angles of attack corresponding to the Reynolds Number Re = 2.02 x 105. These experimental results revealed the complex nature of the downstream near wake characteristics featuring substantial asymmetry arising out of the incoherent flow separations prevailing over the suction and the pressure sides of the airfoil. Based on the experimental results, it is found that the wake width and the downstream velocity ratio decrease with an increase in the angle of attack. Nonetheless, the dissipation length and downstream velocity ratio increases proportionally in the downstream direction. Additionally, attempts were made to understand the physical nature of the near wake characteristics at 1C, 2C, 3C and 4C downstream locations.

Key Words
downstream velocity ratio; downstream wake velocity; Extended Flat Plate (EFP); trailing-edge serrations; wake intensity

Mano Sekar and Nadaraja Pillai Subramania:Turbulence flow control lab, SASTRA Deemed University, Thanjavur, Tamil Nadu, India

Amjad Ali Pasha:Department of Aerospace Engineering, King Abdulaziz University, Jeddah 21589, Saudi Arabia

Due to the complexity and difficulty in meeting the multiphase flow complexity, similarity, and multiscale characteristics, the mechanism of snow drift is so complicated that the snow deposition prediction is still inaccurate and needs to be far improved. Meanwhile, the validation of prediction methods is also limited due to a lack of field-measured data about snow deposition. To this end, a field measurement activity about snow deposition around a cube with time was carried out, and the snow accumulation process was measured under blowing snow conditions in northwest China. The maximum snow depth, snow profile, and variation in snow depth around the cube were discussed and analyzed. The measured results indicated three stages of snow accumulation around the cube. First, snow is deposited in windward, lateral and leeward regions, and then the snow depth in windward and lateral regions increases. Secondly, when the snow in the windward region reaches its maximum, the downwash flow erodes the snow against the front wall. Meanwhile, snow range and depth in lateral regions have a significant increase. Thirdly, a narrow road in the leeward region is formed with the increase in snow range and depth, which results in higher wind speed and reforming snow deposition there. The field measurement study in this paper not only furthers understanding of the snow accumulation process instead of final deposition under complex conditions but also provides an important benchmark for validating prediction methods.

Key Words
blowing snow; field measurement; snow accumulation process; snow deposition around a cube; snowdrift

Wenyong Ma:1)State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures,Shijiazhuang Tiedao University,Shijiazhuang, Hebei, 050043, China
2)Innovation Center for Wind Engineering and Wind Energy Technology of Hebei Province, Hebei, 050043, China
3)School of Civil Engineering, Shijiazhuang Tiedao University, Shijiazhuang, Hebei, 050043, China

Sai Li and Zihan Cui:School of Civil Engineering, Shijiazhuang Tiedao University, Shijiazhuang, Hebei, 050043, China

Xuanyi Zhou:State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, Shanghai, 200092, China

Yuanchun Sun:China Railway Design Corporation, Tianjin, 300251, China

Ziqi Tang:Shijiazhuang No.2 High School, Shijiazhuang, Hebei, 050057, China

To ensure the wind stability of a long-span suspension bridge during deck erection under skew wind, based on the aerostatic and self-excited aerodynamic force models under skew wind, a computational approach of refined flutter analysis for long-span bridges under skew wind is firstly established, in which the effects of structural nonlinearity, the static wind action and full-mode coupling etc are fully considered, and the corresponding computational procedure is programmed. By taking the Runyang suspension bridge over the Yangtze River as example, the flutter stability of the bridge in completion under skew wind is then analyzed with the aerodynamic parameters of a similar bridge deck measured from the sectional model wind tunnel test under skew wind. Finally, through simulating the girder segments erected symmetrically from the midspan to towers, from the towers to midspan and simultaneously from the towers and midspan to the quarter points, respectively, the evolutions of flutter stability limits during the deck erection under skew wind are investigated numerically, the favorable aerodynamically deck erection sequence is proposed, and the influences of skew wind and static wind effect on the flutter stability of suspension bridge under construction are ascertained.

Key Words
deck erection sequence; flutter stability; long-span suspension bridge; skew wind; static wind effect

Xin-Jun Zhang:1)College of Civil Engineering, Zhejiang University of Technology, Hangzhou, 310023, P.R. China
2)Key Laboratory of Civil Engineering Structures & Disaster Prevention and Mitigation Technology of Zhejiang Province,
Hangzhou, 310023, P.R. China

Fu-Bing Ying, Chen-Yang Zhao and Xuan-Rui Pan:College of Civil Engineering, Zhejiang University of Technology, Hangzhou, 310023, P.R. China

In this study, a generalized three-degree-of-freedom (3-DoF) analytical model is formulated to predict linear aerodynamic instabilities of a prism under quasi-steady (QS) conditions. The prism is assumed to possess a generic cross-section exposed to turbulent wind flow. The 3-DoFs encompass two orthogonal horizontal directions and rotation about the prism body axis. Inertial coupling is considered to account for the non-coincidence of the mass center and the rotation center. The aerodynamic force coefficients—drag, lift, and moment—depend on the Reynolds number based on relative flow velocity, angle of attack, and the angle between the wind and the cable. Aerodynamic forces are linearized with respect to the static equilibrium configuration and mean wind velocity. Routh-Hurwitz and Liénard and Chipart criteria are used in the eigenvalue problem, yielding an analytical solution for instabilities in galloping and static divergence types. Additionally, the minimum structural damping and stiffness required to prevent these instabilities are numerically determined. The proposed 3-DoF instability model is subsequently applied to a conductor with ice accretion and a full-scale dry inclined cable. In comparison to existing models, the developed model demonstrates superior prediction accuracy for unstable regions compared with results in wind tunnel tests.

Key Words
aerodynamic damping; aerodynamic stiffness; galloping; quasi-steady; static divergence; three degrees-offreedom

Cristoforo Demartino:1)Zhejiang University - University of Illinois at Urbana Champaign Institute, Zhejiang University, Haining 314400, Zhejiang, PR China
2)Department of Civil and Environmental Engineering,
University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA

Zhen Sun:Construct-ViBest, Faculty of Engineering (FEUP), Univ. of Porto, Porto, Portugal

Giulia Matteoni:Arup, 13 Fitzroy Street, London W1T 4BQ, United Kingdom

Christos T. Georgakis:Department of Civil and Architectural Engineering, Aarhus University, Aarhus, Denmark

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