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CONTENTS
Volume 36, Number 2, February 2023
 


Abstract
Turbulent wind flow over hilly terrains has been extensively investigated in the scientific literature and main findings have been included in technical standards. In particular, turbulent wind flow over nominally two-dimensional hills is often adopted as a benchmark to investigate wind turbine siting, estimate wind loading, and dispersion of particles transported by the wind, such as atmospheric pollutants, wind-driven rain, windblown snow. Windblown sand transport affects human-built structures and natural ecosystems in sandy desert and coastal regions, such as transport infrastructures and coastal sand dunes. Windblown sand transport taking place around any kind of obstacle is rarely in equilibrium conditions. As a result, the modelling of windblown sand transport over complex orographies is fundamental, even if seldomly investigated. In this study, the authors present a wind-sand tunnel test campaign carried out on a nominally two-dimensional sinusoidal hill. A first test is carried out on a flat sand fetch without any obstacle to assess sand transport in open field conditions. Then, a second test is carried out on the hill model to assess the sand flux overcoming the hill and the morphodynamic evolution of the sand sedimenting over its upwind slope. Finally, obtained results are condensed into a dimensionless parameter describing its sedimentation capability and compared with values resulting from other nominally two-dimensional obstacles from the literature.

Key Words
complex orography; particle image velocimetry; particle tracking velocimetry; sinusoidal hill; wind tunnel; windblown sand

Address
Lorenzo Raffaele:1)Department of Architecture and Design, Politecnico di Torino, Viale Mattioli 39, I-10125, Torino, Italy
2)Environmental and Applied Fluid Dynamics Department, von Karman Institute for Fluid Dynamics,
Waterloosesteenweg 72, B-1640, Sint-Genesius-Rode, Belgium
3)Windblown Sand Modeling and Mitigation Joint Research Group, Italy-France

Gertjan Glabeke and Jeroen van Beeck:Environmental and Applied Fluid Dynamics Department, von Karman Institute for Fluid Dynamics,
Waterloosesteenweg 72, B-1640, Sint-Genesius-Rode, Belgium

Abstract
Tuned liquid dampers (TLDs) are increasingly being used as efficient dynamic vibration absorbers to mitigate windinduced vibration in super high-rise buildings. However, the damping characteristics of screens and the control effectiveness of actual structures must be investigated to improve the reliability of TLDs in engineering applications. In this study, a numerical TLD model is developed using computational fluid dynamics (CFD) and a simulation method for achieving the coupled vibration of the structure and TLD is proposed. The numerical results are verified using shaking table tests, and the effects of the solidity ratio and screen position on the TLD damping ratios are investigated. The TLD control effectiveness is obtained by simulating the wind-induced vibration response of a full-scale structure-TLD system to determine the optimal screen solidity ratio. The effects of the structural frequency, damping ratio, and wind load amplitude on the TLD performance are further analyzed. The TLD damping ratio increases nonlinearly with the solidity ratio, and it increases with the screens towards the tank center and then decreases slightly owing to the hydrodynamic interaction between screens. Full-scale coupled simulations demonstrated that the optimal TLD control effectiveness was achieved when the solidity ratio was 0.46. In addition, structural frequency shifts can significantly weaken the TLD performance. The control effectiveness decreases with an increase in the structural damping ratio, and is insensitive to the wind load amplitude within a certain range, implying that the TLD has a stable damping performance over a range of wind speed variations.

Key Words
computational fluid dynamics; coupled vibration control; damping characteristic; screen; super high-rise building; tuned liquid damper

Address
Zijie Zhou and Zhuangning Xie:State Key Laboratory of Subtropical Building Science, South China University of Technology, Guangzhou, 510640, China

Lele Zhang:1)State Key Laboratory of Subtropical Building Science, South China University of Technology, Guangzhou, 510640, China
2)China Construction Second Engineering Bureau Co. Ltd. South China Company, Shenzhen, 518045, China

Abstract
The present study is performed to find the effect of corner recession on a square plan-shaped tall building. A series of numerical simulations have been carried out to find the two orthogonal wind force coefficients on various model configurations using Computational Fluid Dynamics (CFD). Numerical analyses are performed by using ANSYS-CFX (k-ε turbulence model) considering the length scale of 1:300. The study is performed for 0° to 360° wind angle of attack. The CFD data thus generated is utilised to fit parametric equations to predict alongwind and crosswind force coefficients, Cfx and Cfy. The precision of the parametric equations is validated by employing a wind tunnel study for the 40% corner recession model, and an excellent match is observed. Upon satisfactory validation, the parametric equations are further used to carry out multiobjective optimization considering two orthogonal force coefficients. Pareto optimal design results are presented to propose suitable percentages of corner recession for the study building. The optimization is based on reducing the alongwind and crosswind forces simultaneously to enhance the aerodynamic performance of the building.

Key Words
corner recession; force coefficient; Multiobjective Genetic Algorithm (MOGA); parametric equations; pareto optimal solution; tall building

Address
Arghyadip Das, Rajdip Paul and Sujit Kumar Dalui:Civil Engineering Department, Indian Institute of Engineering Science and Technology,
Shibpur, P.O.- Botanic Garden, Shalimar, West Bengal-711103, Howrah, India

Abstract
Aiming at the problem that fatigue characteristics of metal roof rely on local physical tests and lacks the cyclic load sequence matching with regional climate, this paper proposed a method of constructing the fatigue load spectrum based on integration of wind load model, measured data of long-span metal roof and climate statistical data. According to the turbulence characteristics of wind, the wind load model is established from the aspects of turbulence intensity, power spectral density and wind pressure coefficient. Considering the influence of roof configuration on wind pressure distribution, the parameters are modified through fusing the measured data with least squares method to approximate the actual wind pressure load of the roof system. Furthermore, with regards to the wind climate characteristics of building location, Weibull model is adopted to analyze the regional meteorological data to obtain the probability density distribution of wind velocity used for calculating wind load, so as to establish the cyclic wind load sequence with the attributes of regional climate and building configuration. Finally, taking a workshop's metal roof as an example, the wind load spectrum is constructed according to this method, and the fatigue simulation and residual life prediction are implemented based on the experimental data. The forecasting result is lightly higher than the design standards, consistent with general principles of its conservative safety design scale, which shows that the presented method is validated for the fatigue characteristics study and health assessment of metal roof.

Key Words
fatigue load spectrum; life prediction; metal roof; regional climate characteristic; wind load modelling

Address
Liman Yang, Cong Ye, Xu Yang, Xueyao Yang and Jian-ge Kou:School of Automation Science and Electrical Engineering, Beihang University, Beijing 100191, China


Abstract
The random vibration of saddle membrane structures under wind load is studied theoretically and experimentally. First, the nonlinear random vibration differential equations of saddle membrane structures under wind loads are established based on von Karman's large deflection theory, thin shell theory and potential flow theory. The probabilistic density function (PDF) and its corresponding statistical parameters of the displacement response of membrane structure are obtained by using the diffusion process theory and the Fokker Planck Kolmogorov equation method (FPK) to solve the equation. Furthermore, a wind tunnel test is carried out to obtain the displacement time history data of the test model under wind load, and the statistical characteristics of the displacement time history of the prototype model are obtained by similarity theory and probability statistics method. Finally, the rationality of the theoretical model is verified by comparing the experimental model with the theoretical model. The results show that the theoretical model agrees with the experimental model, and the random vibration response can be effectively reduced by increasing the initial pretension force and the rise-span ratio within a certain range. The research methods can provide a theoretical reference for the random vibration of the membrane structure, and also be the foundation of structural reliability of membrane structure based on wind-induced response.

Key Words
experimental investigation; FPK method; random vibration; saddle membrane structures; wind-induced response

Address
Rongjie Pan:1)School of Civil Engineering, Guangzhou University, Guangzhou, 510006, China 2)Guangdong Provincial Key Laboratory of Earthquake Engineering and Applied Technology, Guangzhou University,
Guangzhou 510006, China

Changjiang Liu:1)School of Civil Engineering, Guangzhou University, Guangzhou, 510006, China
2)School of Civil Engineering, Fuzhou University, Fuzhou, 350116, China

Dong Li:School of Civil Engineering, Fuzhou University, Fuzhou, 350116, China

Yuanjun Sun:1)School of Civil Engineering, Guangzhou University, Guangzhou, 510006, China 2)Guangdong Provincial Key Laboratory of Earthquake Engineering and Applied Technology, Guangzhou University,
Guangzhou 510006, China

Weibin Huang:1)School of Civil Engineering, Guangzhou University, Guangzhou, 510006, China 2)Guangdong Provincial Key Laboratory of Earthquake Engineering and Applied Technology, Guangzhou University,
Guangzhou 510006, China

Ziye Chen:1)School of Civil Engineering, Guangzhou University, Guangzhou, 510006, China 2)Guangdong Provincial Key Laboratory of Earthquake Engineering and Applied Technology, Guangzhou University,
Guangzhou 510006, China


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