Effect of Hanger Flexibility on Dynamic Response of Suspension Bridges
Publication: Journal of Engineering Mechanics
Volume 136, Issue 12
Abstract
Linearized continuum models of a suspended span with unloaded backstays and of a symmetric three-span suspension bridge are used to study the effects of the flexibility of the hangers on the vertical vibrations of suspension bridges. The models include elastic parabolic cables, flexible distributed hangers with variable length, and a stiffening girder represented by an elastic beam. It is shown that the free vibrations of a suspended span with unloaded backstays are controlled by five dimensionless parameters, while six dimensionless parameters control the response of a symmetric three-span suspension bridge. The results indicate that the flexibility of the hangers has a significant effect on the natural frequencies of the higher modes only when the relative stiffness of the girder is very high. The effects of hanger flexibility on the response of a suspension bridge to localized impulsive loads are also found to be small. These findings confirm the traditional, albeit previously untested, assumption of inextensible hangers. Finally, the threshold amplitudes of free vibrations that would result in the incipient slackening of the hangers are determined.
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Acknowledgments
The work described here was initiated while J. Turmo was at the University of California, San Diego on sabbatical leave from the University of Castilla-La Mancha. The support from the Fulbright Commission, the Spanish Ministry of Education, the Spanish Ministry of Science and Technology (Grant Nos. UNSPECIFIEDBIA2006-15471-C02-02, UNSPECIFIEDBIA2009-13056) and the Junta de Comunidades de Castilla-La Mancha (Grant No. UNSPECIFIEDPII2I09-0129-4085) is acknowledged.
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Published In
Journal of Engineering Mechanics
Volume 136 • Issue 12 • December 2010
Pages: 1444 - 1459
Copyright
© 2010 ASCE.
History
Received: Jul 10, 2009
Accepted: Apr 19, 2010
Published online: Apr 22, 2010
Published in print: Dec 2010
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