Aerodynamic stability of bridges

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Virginia Polytechnic Institute


The failure of the Tacoma Narrows Bridge in November 1940 was a major course of the beginning of research on the Aerodynamic Stability of Suspension Bridges. Wind has wrecked suspension bridges for over a century but the underlying cause, an increasing harmonic amplitude due to wind, has been ignored until recently.

For many years bridges have been designed to withstand horizontal wind pressure, but the lift force and the overturning moment due to wind have been overlooked. This investigation, in part, was conducted so that aerodynamic coefficients of certain bridge sections not heretofore investigated could be determined. With data from these tests engineers can determine beforehand whether the sections, if used, will be safe against uplifting, sliding, overturning, and of building up oscillations of catastrophic proportions.

The second part of this thesis is devoted to the determination of the torsional oscillation effects in order to predict the dynamic wind characteristics of bridge sections. The dynamic tests are necessary to verify the analytical predictions obtained from the static tests and are valuable in obtaining the aerodynamic constants necessary for the complete solution of the bridge analysis.