CONSIDERATIONS ABOUT FREE VIBRATION ON BRIDGES
PATRICIA ALMEIDA LIPENER1; Reyolando M.L.R.F. Brasil1
1 USP
doi:10.20906/CPS/CILAMCE2017-0024
Resumo
Bridges are structures sometimes referred as works of art or special works, used on routes and roads that allow vehicles to cross natural or artificial obstacles, such as rivers. Such constructions are built considering the efforts to which they will be submitted and their distribution in the structure. Furthermore, it is necessary to assess their natural frequencies of vibration. In the present study some effects were analyzed related to the vibrations of grid bridges and viaducts resulting from changes in stiffness and mass in these structures. This analysis was made considering that excessive vibrations are not consistent with human comfort and bridge durability. For the structure, it is interesting to get away from the resonance effect, which occurs when the excitation frequency matches one of the natural frequencies of oscillation of the system. This leads to oscillation with increasing amplitudes which may cause even the ruin. In order to study several models, three different design situations were adopted: superstructure with varying heights of beams and crossbeams, from which it was possible to conclude that the height of the beams has more impact on the undamped natural frequency of the structure than the crossbeams; small defects or damage to the structure and the effect of a ruptured beam in which its undamped natural frequencies were compared. The analysis were performed using the Finite Element Method, using the SAP2000 commercial program.
Palavras-chave: Bridges; girders; crossbeams