Variation of eigen-properties of a PSC bridge due to prestressing force

초록

Variations of the natural frequency of a prestressed concrete (PSC) girder bridge due to the applied prestressing force are investigated. A finite element formulation for the undamped dynamic motion of a beam-tendon system is derived based on the principle of virtual work. The linear geometric stiffness component of a beam due to the tendon force and that of a taut string due to the prestressing force are separately added to the bending stiffness of the beam. The proposed dynamic equation of motion has been verified through a comparison of the analytical results with those obtained from the results of laboratory experiments available in the literature, which shows significant variation in the natural frequencies due to the prestressing force. The proposed algorithm has been applied to the analysis of actual PSC girder bridges with prestressing. The analytical results show that the variation of the first natural frequency due to the prestressing force is negligibly small in actual PSC bridges, since the added stiffness due to the prestressing is negligible in actual applications.