THEORETICAL ANALYSE OF VIBRATION TIMBER FOOTBRIDEGES

Abstract

The timber possesses high mechanical resistance and lightness. Activities of walking, running and jumping can produce excitements undesirable dynamic, phenomenon of the resonance due to dynamic forces induced by pedestrians, in case of structures present natural frequency inside of the band of step frequency. The dynamic evaluation of the footbridges is necessary to verify the level of human comfort and adaptation when submitted to the pedestrians moving load. The objective of this paper is to be carried out the theoretical dynamic analyses of timber footbridges in structural system in beams through guidelines, with span varying from 5 to 35 m, of 1 in 1 m, widths of 150 and 200 cm, class of resistance of the timber C40 and C60. The timber footbridges were projected using the guidelines of the brazilian NBR 7190 (1997) and NBR 7188 (1982). The results theoretical were compared to the guidelines contained in the international BS 5400, Eurocode 5, ISO 10137, Bro, SIA, AASHTO and OHBDC. It was ended that the current brazilian guideline needs of revisions that take into account the level of human comfort due to the vibrations induced by pedestrians. Keywords: vibrations in the vertical and lateral directions, timber footbridges, pedestrians walking and running, dynamics forces, human comfort.