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Structural Engineering and Mechanics
  Volume 74, Number 4, May25 2020 , pages 495-502

Effects of prestressing force on natural frequency of prestressed concrete beams considering self-weight
Soobong Shin, Hokyoung Lee and Jong-Han Lee

    This study investigated the effects of prestressing force on the natural frequency of concrete beams considering changes in the self-weight of the beam. For this, a finite element formulation was derived to account for the increase in the stiffness of a beam-tendon system due to the axial force and deformation induced by prestressing of the tendon. The developed finite element formulation was validated with the data obtained in laboratory experiments. The experimental natural frequencies of the small prestressed concrete (PSC) beam specimens were consistent with those obtained using the proposed method. The first natural frequency increased almost linearly as the prestressing force increased. The proposed method was then applied to four actual PSC bridges typically employed in the field. Different from the laboratory specimens, the first natural frequencies of the actual PSC bridges barely changed or increased with increasing prestressing force. The results of an analytical parametric study showed that the increase in the natural frequency strongly depended on the magnitude of the prestressing force relative to the total weight of the structure. Thus, the variation in the natural frequencies of the actual PSC bridges with high total weight relative to the prestressing force was negligible due to the application of the prestressing force.
Key Words
    prestressed concrete bridge; prestressing force; self-weight; natural frequency; geometric stiffness
Soobong Shin,and Jong-Han Lee: Department of Civil Engineering, Inha University, 100 Inha-ro, Michuhol-gu, Incheon 22212, Korea
Hokyoung Lee: Korea Bridge Institute Co., 252 Gilju-ro, Wonmi-gu, Bucheon, Gyeonggido 14548, Korea

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