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CONTENTS
Volume 22, Number 2, February 2016
 

Abstract
Hurricanes are among the most costly natural hazards to impact buildings in coastal regions. Building roofs are designed using the wind load provisions of building codes and standards and, in the case of large buildings, wind tunnel tests. Wind permeable roof claddings like roof pavers are not well dealt with in many existing building codes and standards. The objective of this paper is to develop simple guidance in code format for design of loose-laid roof pavers. Large-scale experiments were performed to investigate the wind loading on concrete roof pavers on the flat roof of a low-rise building in Wall of Wind, a large-scale hurricane testing facility at Florida International University. They included wind blow-off tests and pressure measurements on the top and bottom surfaces of pavers. Based on the experimental results simplified guidelines are developed for design of loose-laid roof pavers against wind uplift. The guidelines are formatted so that use can be made of the existing information in codes and standards such as American Society of Civil Engineering (ASCE) 7-10 standard\'s pressure coefficients for components and cladding. The effects of the pavers\' edge-gap to spacer height ratio and parapet height to building height ratio are included in the guidelines as adjustment factors.

Key Words
design guidelines; roof pavers; large-scale testing; wind uplift

Address
Maryam Asghari Mooneghi: Advanced Technology and Research, Arup, San Francisco, CA, USA
Peter Irwin and Arindam Gan Chowdhury: Department of Civil and Environmental Engineering/International Hurricane Research Center, Florida International University, Miami, FL, USA

Abstract
Long-span suspension bridges have evolved through the years and with them, the bridge girder decks improved as well, changing their shapes from standard box-deck girders to twin box and multi-box decks sections. The aerodynamic characteristics of the new generation of twin and multiple-decks are investigated nowadays, to provide the best design wind speeds and the optimum dimensions such bridges could achieve. The multi-box Megane bridge deck is one of the new generation bridge decks, consisting of two side decks for traffic lanes and two middle decks for railways, linked between them with connecting beams. Three-dimensional CFD simulations were performed by employing the Large Eddy Simulation (LES) algorithm with a standard Smagorinsky subgrid-scale model, for Re = 9.3 x 107 and angles of attack a = -4, -2, 0, 2 and 4. Also, a wind tunnel experiment was performed for a scaled model, 1:80 of the Megane bridge deck section, for Re = 5.1 x 105 and the aerodynamic static coefficients were found to be in good agreement with the results obtained from the CFD-LES model. However the aerodynamic coefficients determined individually, from the CFD-LES model, for each of the traffic and railway decks of the Megane bridge, varied significantly, especially for the downstream traffic deck. Also the pressure distribution and the effect of the spacing between the connecting beams, on the wind speed profiles showed a slight increase in turbulence above the downstream traffic and railway decks.

Key Words
multi-box Megane bridge deck; aerodynamic coefficients; CFD simulation; wind tunnel experiments; wind flow patterns

Address
Elena Dragomirescu, Zhida Wang and Michael S. Hoftyzer: Department of Civil Engineering, University of Ottawa, 161 Louis Pasteur, Ottawa, K1N 6N5, ON, Canada

Abstract
Across-wind aerodynamic damping ratios are identified from the wind-induced acceleration responses of 15 aeroelastic models of rectangular super-high-rise buildings in various simulated wind conditions by using the random decrement technique. The influences of amplitude-dependent structural damping ratio and natural frequency on the estimation of the aerodynamic damping ratio are discussed and the identifying method for aerodynamic damping is improved at first. Based on these works, effects of turbulence intensity Iu, aspect ratio H/B, and side ratio B/D on the across-wind aerodynamic damping ratio are investigated. The results indicate that turbulence intensity and side ratio are the most important factors that affect across-wind aerodynamic damping ratio, whereas aspect ratio indirectly affects the aerodynamic damping ratio by changing the response amplitude. Furthermore, empirical aerodynamic damping functions are proposed to estimate aerodynamic damping ratios at low and high reduced speeds for rectangular super-high-rise buildings with an aspect ratio in the range of 5 to 10, a side ratio of 1/3 to 3, and turbulence intensity varying from 1.7% to 25%.

Key Words
high-rise building; aerodynamic damping; aeroelastic model; wind tunnel test; wind-induced vibration

Address
Y. Quan, H.L. Cao and M. Gu: State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China

Abstract
Super long-span bridges provide people with great convenience, but they also bring traffic safety problems caused by strong wind owing to their high decks. In this paper, the large eddy simulation together with dynamic mesh technology in computational fluid dynamics (CFD) is used to explore the mechanism of a moving vehicle\'s transient aerodynamic force in crosswind, the regularity and mechanism of the vehicle

Key Words
CFD (computational fluid dynamics); bluff body; cable-stayed bridge; large eddy simulation (LES); aerodynamic problem

Address
Lin Ma and Dajun Zhou: Department of Civil Engineering, University of Hohai, No.1 Xikang Road, Nanjing, Jiangsu 210098, China
Wanshui Han, Jun Wu and Jianxin Liu: Department of Bridge Engineering, University of Chang\'an, Middle of S.2nd Ring Road, Xi\'an, Shanxi 710064, China


Abstract
A wind velocity power spectrum (WVPS) with high fidelity is extremely important for accurate prediction of structural buffeting response. WVPS heavily depends on the geographical locations, local terrains and topographies. Hence, field measurement of wind characteristics may be the unique way to obtain the accurate WVPS for a specific region. In this paper, a systematic analysis and discussions of existing WVPSs were performed. Six recorded strong wind data from the structural health monitoring systems (SHMS) of Runyang Suspension Bridge (RSB) and Sutong Cable-stayed Bridge (SCB) in Jiangsu Province of China were selected for analysis. The measured and pre-processed wind velocity data was first transformed from time domain to frequency domain to obtain the measured spectrum. The spectrum for each strong wind was then fitted using the nonlinear least square method and compared with both the fitted spectrum from statistical analysis and the recommended spectrum in specifications. The modified Kaimal spectrum was proved to be the \"best\" choice for the coastal area of East Jiangsu Province. Finally, a suitable WVPS formula fit for the coastal area of East Jiangsu Province was presented based on the modified Kaimal spectrum. Results in this study provide a more accurate and reliable WVPS for wind-resistant design of engineering structures in the coastal area of East Jiangsu Province.

Key Words
wind velocity; power spectrum; strong wind; coastal area of East Jiangsu Province; structural health monitoring

Address
Hao Wang and Tianyou Tao: Key Laboratory of C&PC Structures of Ministry of Education, Southeast University, No. 2 Sipailou,Nanjing 210096, China
Teng Wu: Department of Civil, Structural and Environmental Engineering, University at Buffalo, State University of New York, Buffalo, NY 14126, USA


Abstract
The paper concerns with the method and results of wind tunnel investigations of the Strouhal number (St) of a stationary iced cable model of cable-supported bridges with respect to different angles of wind attack. The investigations were conducted in the Climatic Wind Tunnel Laboratory of the Czech Academy of Sciences in Telč. The methodology leading to the experimental icing of the inclined cable model was prepared in a climatic section of the laboratory. The shape of the ice on the cable was registered by a photogrammetry method. A section of an iced cable model with a smaller scale was reproduced with a 3D printing procedure for subsequent aerodynamic investigations. The St values were determined within the range of the Reynolds number (Re) between 2.4•104 and 16.5•104, based on the dominant vortex shedding frequencies measured in the wake of the model. The model was oriented at three principal angles of wind attack for each of selected Re values. The flow regimes were distinguished for each model configuration. In order to recognize the tunnel blockage effect the St of a circular smooth cylinder was also tested. Good agreement with the reported values in the subcritical Re range of a circular cylinder was obtained. The knowledge of the flow regimes of the airflow around an iced cable and the associated St values could constitute a basis to formulate a mathematical description of the vortex-induced force acting on the iced cable of a cable-supported bridge and could allow predicting the cable response due to the vortex excitation phenomenon.

Key Words
bridge cable; ice accretion; Strouhal number; angle of attack; vortex shedding frequency

Address
Piotr Gorski and Marcin Tatara: Department of Road and Bridges, Faculty of Civil Engineering and Architecture, Opole University of Technology, 45-061 Opole, Katowicka 48, Poland
Stanislav Pospisil and Sergej Kuznetsov:Institute of Theoretical and Applied Mechanics, Academy of Sciences of the Czech Republic, Czech Republic
Ante Marusic:Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, Croatia


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