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CONTENTS
Volume 7, Number 1, January 2004
 

Abstract
Numerical simulation of flow past two-dimensional hill and valley is presented. Application of three turbulence models - the standard and modified (Kato-Launder) k- e models and standard k- w model - is discussed. The computational methodology is briefly described. The mean velocity and turbulence intensity profiles, obtained from numerical simulations of flow past the hill, are compared with the experimental data acquired in a boundary-layer wind tunnel at Colorado State University. The mean velocity, turbulence kinetic energy and Reynolds shear stress profiles from numerical simulations of flow past the valley are compared with published experimental data. Overall, the results of simulations employing the standard k- e model were found to be in a better agreement with the experimental data than those obtained using the modified k- e model and the k- w model.

Key Words
numerical simulation; k- e model; k- w model; ASCE 7-98; wind speed-up ratio.

Address
Wind Engineering and Fluids Laboratory, Engineering Research Center, Colorado State University, Fort Collins, Co 80523, U.S.A.

Abstract
A method of numerical analysis without conducting 3D wind tunnel model tests was examined in our previous study for predicting vortex-induced oscillation of bridge girders with span-wise varying geometry. The aerodynamic damping forces measured for plural wind tunnel 2D models were used in the analysis. A further study was conducted to examine the precision of solution obtained by this method. First, the responses of vortex-induced oscillation of two rocking models and a taut-strip bridge girder model with span-wise varying geometry were measured. Next, the responses of these models were numerically analyzed by means of this method, and then a comparison was made between the obtained Vr-A- da contour diagram of each 3D model in the wind tunnel test and the diagram in the numerical analysis. Since close correlations were observed between each two Vr-A- da diagrams obtained in the model test and in the analysis in cases where the 3D model did not have strong three-dimensionality, our findings revealed that the predicted solution proved to be reasonably accurate.

Key Words
vortex-induced oscillation; bridge girders with span-wise varying geometry; 3D numerical analysis; precision of solution; wind tunnel model tests.

Address
Takehiko Harada, Takeshi Yoshimura, Takahisa Tanaka, Yoji Mizuta, Takafumi Hashiguchi; Department of Civil Eng., Kyushu Sangyo University, Higashi-Ku, Fukuoka, 813-8503, JapanrnMakoto Sudo; Ing?rosec Co., Ltd., 6-3-1 Nishishinjuku, Shinjuku-Ku, Tokyo, 160-0023, JapanrnMasao Miyazaki; Sumitomo Heavy Industries, Ltd., Shinagawa-Ku, Tokyo, 141-8686, Japan

Abstract
This study has focused on aerodynamics for a wind-resistance design about the single and tandem box girder sections to realize a super-long span bridge in the near future. Three-dimensional static analysis of flows around the fundamental single and tandem box girder sections with fairing is carried out by means of the IBTD/FS finite element technique with LES turbulence model. As the results of the analysis, computations have verified aerodynamic characteristics of both sections by the histories of aerodynamic forces, the separation and reattachment flow patterns and the surface pressure distributions. The relationship between the section shapes and the aerodynamic characteristics is also investigated in both sections. And the mechanism about the generation of fluctuating aerodynamic forces is discussed.

Key Words
CFD; LES; FEM; box girder section; fairing; aerodynamics.

Address
Shigeru Watanabe; Research & Development Headquarters, Mitsui Engineering & Shipbuilding Co., Ltd., Okayama, JapanrnHiroo Inoue; Structure & Logistic Systems Headquarters, Mitsui Engineering & Shipbuilding Co., Ltd., Tokyo, JapanrnKoichiro Fumoto; Public Works Research Institute Independent Administrative Institution, Ibaraki, Japan

Abstract
An analysis refinement of the Messina Strait suspension bridge project has been recently required, concerning mainly the yaw angle effects on the multi-box deck section aerodynamics and the vortex shedding at low reduced velocities V*. In particular the possible interaction of the axial flow with the large cross beams has been investigated. An original test rig has been designed at this purposernallowing for both forced motion and free motion aero elastic tests, varying the average angle of attack a and the deck yaw angle b. The hydraulic driven test rig allowed for both dynamic and stationary tests so that both the stationary coefficients and the flutter derivatives have been evaluated for each yaw angle. Specific free motion tests, taking advantage from the aeroelastic features of the section model, allowed also the study of the vortex shedding induced phenomena.

Key Words
wind tunnel; bridge aeroelasticity; yaw angle; flutter derivatives; vortex induced vibrations.

Address
Mechanical Department, Politecnico di Milano, Via La Masa 34 Milano, Italy

Abstract
Aerostatic instability of a suspension bridge may suddenly appears when the deformed shape of the structure produces an increase in the value of the three components of displacement-dependent wind loads distributed in the structure. This paper investigates the aerostatic stability of suspension bridges using an advanced nonlinear method based on the concept of limit point instability. Particular attention is devoted to aerostatic stability analysis of symmetrical suspension bridges. A long-span symmetrical suspension bridge (Hu Men Bridge) with a main span of 888 m is chosen for analysis. It is found that the initial configuration (symmetry or asymmetry) may affect the instability configuration of structure. A finite element software for the nonlinear aerostatic stability analysis of cable-supported bridges (NASAB) is presented and discussed. The aerostatic failure mechanism of suspension bridges is also explained by tracing aerostatic instability path.

Key Words
suspension bridges; aerostatic stability; three components of displacement-dependent wind loads; geometric nonlinearity; aerostatic failure mechanism

Address
Department of Bridge Engineering, Tongji University, Shanghai, 200092, China


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