Influence of Ground Motion Frequency Characteristics on Longitudinal Seismic Response of Single Tower Cablestayed Bridges

Abstract:

Based on a real singletower cablestayed bridge, both velocity pulses and real earthquake waves are used to study the influence of ground motion frequency characteristics on seismic behavior of singletower cablestayed bridges. The analysis results show that long duration velocity pulse contained by nearfault ground motions have significant effects on the seismic response of singletower cablestayed bridges. Especially, when the ratio of peak ground velocity (Vp) to peak ground acceleration (ap) is large, the period of velocity pulses gets close to the period of 1st vertical bending mode of the bridge, and thus the response of the tower, girder, cables and bearings increases significantly with possibility that cable relaxation and end span uplift might occur. The results show that cable relaxation and end span uplift have a significant influence on the response of the structure like deck displacement, cable axial force and bearing vertical reactions. The response of the deck displacement and cable axial force would possibly be underestimated if neglecting influence of cable relaxation and end span uplift.

Key words:bridge engineering; single tower cablestayed bridge; ground motion frequency characteristics; seismic behavior; cable relaxation; end span uplift