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CONTENTS
Volume 8, Number 3, May 2005
 

Abstract
Two identical tall building models with square cross-sections are experimentally studied in a wind tunnel with high-frequency-force-balance (HFFB) technique to investigate the interference effects on wind loads and dynamic responses of the interfered building. Another wind tunnel test, in which the interfered model is an aeroelastic one, is also carried out to further study the interference effects. The results from the two kinds of tests are compared with each other. Then the influences of turbulence in oncoming wind on dynamic interference factors are analyzed. At last the artificial neural networks method is used to deal with the experimental data and the along-wind and across-wind dynamic interference factor ( IFdx & IFdy ) contour maps are obtained, which could be used as references for wind load codes of buildings.

Key Words
tall building; aerodynamic interference; HFFB technique; aeroelastic model; neural networks.

Address
State Key Laboratory for Disaster Reduction in Civil Engineering,Tongji University, Shanghai 20092, P. R. China

Abstract
Wind-induced mean and dynamic interference effects of tall buildings are studied in detail by a series of wind tunnel tests in this paper. Interference excitations of several types of upwind structures of different sizes in different upwind terrains are considered. Comprehensive interference characteristics are investigated by artificial neural networks and correlation analysis. Mechanism of the wakes vortex-induced resonance is discussed, too. Measured results show significant correlations exist in the distributions of the interference factors of different configurations and upwind terrains and, therefore, a series of relevant regression equations are proposed to simplify the complexity of the multi-parameter wind induced interference effects between two tall buildings.

Key Words
tall building; interference effects; wind load; correlation method; regression analysis.

Address
State Key Laboratory for Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, People\'s Republic of China

Abstract
This paper describes the application of a wireless data acquisition system to monitor wind pressures and velocities with absolute pressure sensors and an anemometer. The system was developed for future deployment, as part of a research effort currently underway to instrument coastal homes in Florida to monitor roof wind pressures during hurricanes. The proposed wireless system will replace the current system that involves a large amount of hardwired connections from the sensors to the data processing unit that requires labor intensive wiring and preparation of the home. The paper describes comparison studies and field tests to assess the performance of the system. The new system offers the advantages of light hardware, ease of installation, capacity for 48 hours of continuous data acquisition, good frequency and amplitude responses, and a relatively simple maintenance. However, the tests also show that the shape of the shell that has been previously used to protect the sensors might interfere with the proper measurement of the pressures.

Key Words
wireless sensing; hurricane wind loads; coastal monitoring; pressure transducer.

Address
Florida Institute of Technology, 150 W. University Blvd, Melbourne, FL 32901, USA

Abstract
Tall buildings under wind action usually oscillate simultaneously in the along-wind and across-wind directions as well as in torsional modes. While several procedures have been developed for predicting wind-induced loads and responses in along-wind direction, accurate analytical methods for estimating across-wind and torsional response have not been possible yet. Simplified empirical formulas for estimation of the across-wind dynamic responses of rectangular tall buildings are presented in this paper. Unlike established empirical formulas in codifications, the formulas proposed in this paper are developed based on simultaneous pressure measurements from a series of tall building models with various side and aspect ratios in a boundary layer wind tunnel. Comparisons of the across-wind responses determined by the proposed formulas and the results obtained from the wind tunnel tests as well as those estimated by two well-known wind loading codes are made to examine the applicability and accuracy of the proposed simplified formulas. It is shown through the comparisons that the proposed simplified formulas can be served as an alternative and useful tool for the design and analysis of wind effects on rectangular tall buildings.

Key Words
tall building; wind effect; wind-induced response; wind tunnel test.

Address
Shuguo Liang and Lianghao Zou; School of Civil and Building Engineering, Wuhan University, Wuhan 430072, P. R. ChinarnQ. S. Li and J. R. Wu; Department of Building and Construction, City University of Hong Kong, Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong

Abstract
Wind uplift rating of roofing systems is based on standardized test methods. Roof specimens are placed in an apparatus with a specified table size (length and width) then subjected to the required wind load cycle. Currently, there is no consensus on the table size to be used by these testing protocols in spite of the fact that the table size plays a significant role in wind uplift performance. Part I of this paper presented a study with the objective to investigate the impact of table size on the performance of roofing systems. To achieve this purpose, extensive numerical experiments using the finite element method have been conducted and benchmarked with results obtained from the experimental work. The present contribution is a continuation of the previous research and can be divided into two parts: (1) Undertake additional numerical simulations for wider membranes that were not addressed in the previous works. Due to the advancement in membrane technology, wider membranes are now available in the market and are used in commercial roofing practice as it reduces installation cost and (2) Formulate a logical step to combine and generalize over 400 numerical tests and experiments on various roofing configurations and develop correction factors such that it can be of practical use to determine the wind uplift resistance of roofs.

Key Words
wind uplift; roofing system; test method; numerical model; thermoplastic; thermoset; modified bituminous; fastener force and correction factor.

Address
A. Baskaran; National Research Council Canada, Ottawa, Ontario, Canada, K1A 0R6, CanadarnS. Molleti; Department of Civil Engineering, University of Ottawa, Ottawa, Ontario, Canada, K1N 6N5, Canada


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