Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Department

Civil Engineering

First Advisor's Name

Arindam Gan Chowdhury

First Advisor's Committee Title

Committee Co-Chair

Second Advisor's Name

Peter Irwin

Second Advisor's Committee Title

Committee Co-Chair

Third Advisor's Name

Amir Mirmiran

Third Advisor's Committee Title

Committee Member

Fourth Advisor's Name

Ioannis Zisis

Fourth Advisor's Committee Title

Committee Member

Fifth Advisor's Name

Irtishad Ahmad

Fifth Advisor's Committee Title

Committee Member

Sixth Advisor's Name

Nakin Suksawang

Sixth Advisor's Committee Title

Committee Member

Keywords

Bridge Aerodynamics, Twin-Deck Bridges, Vortex Shedding, Buffeting Loads, Reynolds Number, Gap Width Effect, Turbulence Effects, Aeroelastic Testing, Sectional Model

Date of Defense

3-25-2015

Abstract

Long-span bridges are flexible and therefore are sensitive to wind induced effects. One way to improve the stability of long span bridges against flutter is to use cross-sections that involve twin side-by-side decks. However, this can amplify responses due to vortex induced oscillations.

Wind tunnel testing is a well-established practice to evaluate the stability of bridges against wind loads. In order to study the response of the prototype in laboratory, dynamic similarity requirements should be satisfied. One of the parameters that is normally violated in wind tunnel testing is Reynolds number. In this dissertation, the effects of Reynolds number on the aerodynamics of a double deck bridge were evaluated by measuring fluctuating forces on a motionless sectional model of a bridge at different wind speeds representing different Reynolds regimes. Also, the efficacy of vortex mitigation devices was evaluated at different Reynolds number regimes.

One other parameter that is frequently ignored in wind tunnel studies is the correct simulation of turbulence characteristics. Due to the difficulties in simulating flow with large turbulence length scale on a sectional model, wind tunnel tests are often performed in smooth flow as a conservative approach. The validity of simplifying assumptions in calculation of buffeting loads, as the direct impact of turbulence, needs to be verified for twin deck bridges. The effects of turbulence characteristics were investigated by testing sectional models of a twin deck bridge under two different turbulent flow conditions.

Not only the flow properties play an important role on the aerodynamic response of the bridge, but also the geometry of the cross section shape is expected to have significant effects. In this dissertation, the effects of deck details, such as width of the gap between the twin decks, and traffic barriers on the aerodynamic characteristics of a twin deck bridge were investigated, particularly on the vortex shedding forces with the aim of clarifying how these shape details can alter the wind induced responses.

Finally, a summary of the issues that are involved in designing a dynamic test rig for high Reynolds number tests is given, using the studied cross section as an example.

Identifier

FI15032184

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