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CONTENTS
Volume 12, Number 2, March 2009
 

Abstract
The Monte Carlo procedure was used to simulate wind load effects on a light-frame low-rise structure of irregular shape and a main wind force resisting system. Two analytical models were studied: rigid-beam and rigid-plate models. The models assumed that roof diaphragms were rigid beam or rigid plate and shear walls controlled system behavior and failure. The parameters defining wall stiffness, including imperfections, were random and included wall stiffness, wall capacity and yield displacements. The effect of openings was included in the simulation via a set of discrete multipliers with uniform distribution. One and two-story buildings were analyzed and the models can be expanded into multiple-floor structures provided that the assumptions made in this paper are not violated.

Key Words
low-rise building; simplified models; wind loads; stochastic analysis.

Address
C. Fischer; Institute of Theoretical and Applied Mechanics,
Academy of Sciences, Prosecka 76, 190 00 Prague 9, Czech Republic
B. Kasal; Department of Civil and Environmental Engineering; Department of Architectural Engineering,
Penn State University, University Park, PA 16802, USA

Abstract
Articulated tower platforms due to its compliant nature are more susceptible to the dynamic effects of wind than conventional fixed platforms. Dynamic response analysis of a double hinged articulated tower excited by low frequency wind forces with random waves is presented in this paper. The exposed super structure of the platform, housing the drilling and production facilities is subjected to mean and fluctuating wind loads, while the submerged portion is acted upon by wind driven waves. The fluctuating component of the wind velocity is modeled by Emil Simiu

Key Words
offshore structures; dynamic response; articulated loading platform; wind driven waves; sea site wind spectrum; compliant tower; nonlinearities; turbulent wind.

Address
Nazrul Islam and Mohd Moonis Zaheer; Department of Civil Engineering, Jamia Millia Islamia, New Delhi-110025, India
Suhail Ahmed; Department of Applied Mechanics, Indian Institute of Technology, Delhi-110016, India

Abstract
A systematic reliability evaluation approach for torsional divergence analysis of long span suspension bridges is proposed, consisting of the first order reliability method and a simplified torsional divergence analysis method. The proposed method was implemented in the deterministic torsional divergence analysis program SIMTDB through a new strategy involving interfacing the proposed method with SIMTDB via a freely available MATLAB software tool (FERUM). A numerical example involving a detailed computational model of a long span suspension bridge with a main span of 888 m is presented to demonstrate the applicability and merits of the proposed method and the associated software strategy. Finally, the most influential random variables on the reliability of long span suspension bridges against torsional divergence failure are identified by a sensitivity analysis.

Key Words
Keywords: torsional divergence; wind effect; structural reliability; suspension bridges; long span structures; displacement-dependent wind loads.

Address
Jin Cheng; Department of Bridge Engineering, Tongji University, Shanghai, 200092, China
Q.S. Li; Department of Building and Construction, City University of Hong Kong, Hong Kong

Abstract
This paper outlines the results of a physical simulation (at a 1:700?-?1:1000 geometric scale) of a thunderstorm downburst. Three different methods are examined in order to generate the time dependent nature of a downburst: directly controlling the fans and via two different types of opening apertures. Similarities are shown to exist between each method, although the results obtained from one approach are favoured since they appear to be independent of the downdraft velocity. Significant run-to-run variations between each experiment are discovered and in general it is found beneficial to interpret the results in terms of 10 run ensemble averages. An attempt to simulate a translating downburst is also undertaken and the results are shown to compare favourably with full-scale data.

Key Words
thunderstorms; downburst; impinging jet; transient simulations.

Address
McConville A. C.; Arup, 13 Fitzroy Street, London, UK
Sterling M. and Baker C. J.; School of Civil Engineering, The University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK

Abstract
The International Hurricane Research Center (IHRC) at Florida International University (FIU) is pursuing research to better understand hurricane-induced effects on residential buildings and other structures through full-scale aerodynamic and destructive testing. The full-scale 6-fan Wall of Wind (WoW) testing apparatus, measuring 4.9?m tall by 7.3?m wide, is capable of generating hurricane-force winds. To achieve windstorm simulation capabilities it is necessary to reproduce mean and turbulence characteristics of hurricane wind flows. Without devices and methods developed to achieve target wind flows, the full-scale WoW simulations were found to be unsatisfactory. To develop such devices and methods efficiently, a small-scale (1:8) model of the WoW was built, for which simulation devices were easier and faster to install and change, and running costs were greatly reduced. The application of such devices, and the use of quasiperiodic fluctuating waveforms to run the WoW fan engines, were found to greatly influence and improve the turbulence characteristics of the 1:8 scale WoW flow. Reasonable reproductions of wind flows with specified characteristics were then achieved by applying to the full-scale WoW the devices and methods found to be effective for the 1:8 scale WoW model.

Key Words
Wall of Wind; full-scale testing; hurricane simulation; turbulence characteristics; fluctuating waveform; small-scale model.

Address
Peng Huang; International Hurricane Research Center (IHRC), Florida International University, 10555 W. Flagler Street, Miami, FL 33174, USA
State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, Shanghai 20092, P. R. China
Arindam Gan Chowdhury, Girma Bitsuamlak and Roy Liu; International Hurricane Research Center (IHRC), Florida International University, 10555 W. Flagler Street, Miami, FL 33174, USA


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