EFFECTS OF LOCAL CABLE VIBRATION ON THE SEISMIC RESPONSE OF CABLE-STAYED BRIDGES

Cable in cable-stayed bridges is flexible in transverse direction.Coupled cable-deck or cable-tower motion may occur under the excitation of earthquake which can affect the energy distribution and damping characteristics of the bridge.It is necessary to take into account the effects of local cable vibration in the seismic response analysis of cable-stayed bridges.Based on substructure and freedom condensation methods,local cable vibration can be incorporated in the dynamic characteristics and seismic response of cable-stayed bridges.A three dimensional finite element program is developed.The effects of local cable vibration on the dynamic characteristics and seismic response of cable-stayed bridge are studied.The results show that the introduction of local cable vibration leads to a decrease in the participation factors of longitudinal modes and remarkable increases in the acceleration,displacement,flexural moment and axial force of deck and tower.The displacements of short cables reduce while those of long cables increase.The dynamic cable tension magnifies.Local cable vibration phenomena are obvious in the time history of cable displacement and tension.