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Structural Engineering and Mechanics
  Volume 28, Number 5, March30 2008, pages 515-524
DOI: http://dx.doi.org/10.12989/sem.2008.28.5.515
 


Effect of prestressing on the first flexural natural frequency of beams
O. R. Jaiswal

 
Abstract
    In this paper the effect of prestressing force on the first flexural natural frequency of beams is studied. Finite element technique is used to model the beam-tendon system, and the prestressing force
is applied in the form of initial tension in the tendon. It is shown that the effect of prestressing force on the first natural frequency depends on bonded and unbonded nature of the tendon, and also on the eccentricity of tendon. For the beams with bonded tendon, the prestressing force does not have any appreciable effect on the first flexural natural frequency. However, for the beams with unbonded tendon, the first natural frequency significantly changes with the prestressing force and eccentricity of the tendon. If the eccentricity of tendon is small, then the first natural frequency decreases with the prestressing force and if the eccentricity is large, then the first flexural natural frequency increases with the prestressing force. Results of the present study clearly indicate that the first natural frequency can not be used as an easy indicator for detecting the loss of prestressing force, as has been attempted in some of the past studies.
 
Key Words
    prestressed beam; flexural natural frequency; bonded and unbonded tendon; prestressing force.
 
Address
O. R. Jaiswal: Dept. of Applied Mechanics, Visvesvaraya National Institute of Technology, Nagpur 440 011, India
 

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