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CONTENTS
Volume 11, Number 1, January 2008
 

Abstract
Interference effects in five square tall buildings arranged in an L- or T-shaped pattern are investigated in the wind tunnel. Mean and fluctuating shear forces, overturning moments and torsional moment are measured on each building with a force balance mounted at its base. Results are obtained at two values of clear separation between adjacent buildings, at half and a quarter building breadth. It is found that strong interference effect exists on all member buildings, resulting in significant modifications of wind loads as compared with the isolated single building case. Sheltering effect is observed on wind loads acting along the direction of an arm of the

Key Words
interference effect; wind loads; sheltering; channeling.

Address
Department of Civil Engineering, University of Hong Kong, Pokfulam Road, Hong Kong

Abstract
This research investigates the adaptive input estimation method applied to the multilayer shearing stress structure. This method is to estimate the values of wind load inputs by analyzing the active reaction of the system. The Kalman filter without the input term and the adaptive weighted recursive least square estimator are two main portions of this method. The innovation vector can be produced by the Kalman filter, and be applied to the adaptive weighted recursive least square estimator to estimate the wind load input over time. This combined method can effectively estimate the wind loads to the structure system to enhance the reliability of the system active performance analysis. The forms of the simulated inputs (loads) in this paper include the periodic sinusoidal wave, the decaying exponent, the random combination of the sinusoidal wave and the decaying exponent, etc. The active reaction computed plus the simulation error is regard as the simulated measurement and is applied to the input estimation algorithm to implement the numerical simulation of the inverse input estimation process. The availability and the precision of the input estimation method proposed in this research can be verified by comparing the actual value and the one obtained by numerical simulation.

Key Words
adaptive input estimation method; shearing stress structure; wind load; Kalman filter.

Address
Department of Power Vehicle and Systems Engineering, Chung Cheng Institute of Technology, National Defense University, Ta-His, Tao-Yuan 33509, Taiwan, R.O.C.

Abstract
Wind and temperature have been shown to be the critical sources causing changes in the modal properties of large-scale bridges. While the individual effects of wind and temperature on modal variability have been widely studied, the investigation about the effects of multiple environmental factors on structural modal properties was scarcely reported. This paper addresses the modeling of the simultaneous effects of wind and temperature on the modal frequencies of an instrumented cable-stayed bridge. Making use of the long-term monitoring data from anemometers, temperature sensors and accelerometers, a neural network model is formulated to correlate the modal frequency of each vibration mode with wind speed and temperature simultaneously. Research efforts have been made on enhancing the prediction capability of the neural network model through optimal selection of the number of hidden nodes and an analysis of relative strength of effect (RSE) for input reconstruction. The generalization performance of the formulated model is verified with a set of new testing data that have not been used in formulating the model. It is shown that using the significant components of wind speeds and temperatures rather than the whole measurement components as input to neural network can enhance the prediction capability. For the fundamental mode of the bridge investigated, wind and temperature together apply an overall negative action on the modal frequency, and the change in wind condition contributes less to the modal variability than the change in temperature.

Key Words
modal variability; environmental effect; wind; temperature; relative strength of effect (RSE); neural network; cable-stayed bridge.

Address
H. F. Zhou, Y. Q. Ni and J. M. Ko; Department of Civil and Structural Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
K. Y. Wong; Bridges and Structures Division, Highways Department, The Hong Kong SAR Government, Hong Kong

Abstract
CFD is applied to evaluate pedestrian wind comfort at outdoor platforms in a high-rise apartment building. Model validation is focused on generic building sub-configurations that are obtained by decomposition of the actual complex building geometry. The comfort study is performed during the design stage, which allows structural design changes to be made for wind comfort improvement. Preliminary simulations are performed to determine the effect of different design modifications. A full wind comfort assessment study is conducted for the final design. Structural remedial measures for this building, aimed at reducing pressure short-circuiting, appear to be successful in bringing the discomfort probability estimates down to acceptable levels. Finally, the importance of one of the main sources of uncertainty in this type of wind comfort studies is illustrated. It is shown that the uncertainty about the terrain roughness classification can strongly influence the outcome of wind comfort studies and can lead to wrong decisions. This problem is present to the same extent in both wind tunnel and CFD wind comfort studies when applying the same particular procedure for terrain relation contributions as used in this paper.

Key Words
numerical simulation; Computational Fluid Dynamics (CFD); pedestrian wind comfort; wind environment; wind nuisance; wind flow; building passage; validation; wind tunnel measurements; sand erosion.

Address
B. Blocken; Building Physics and Systems, Technische Universiteit Eindhoven, P.O. Box 513, 5600 MB Eindhoven, the Netherlands
J. Carmeliet; Building Physics and Systems, Technische Universiteit Eindhoven, P.O. Box 513,
5600 MB Eindhoven, the Netherlands
Laboratory of Building Physics, Katholieke Universiteit Leuven, Kasteelpark Arenberg 40,
3001 Leuven, Belgium

Abstract
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Key Words
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Address
X. G. Hua and Z. Q. Chen; Wind Engineering Research Center, College of Civil Engineering, Hunan University, Changsha, 410082, Hunan, P. R. China
by Shambhu Sharan Mishra; Department of Civil Engineering, NERIST, Nirjuli, Arunachal Pradsh-791109, India
Krishen Kumar and Prem Krishna; Department of Civil Engineering, Indian Institute of Technology, Roorkee-247667, India


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