Transverse failure modes and control strategies of super long-span cable-stayed bridge under extreme earthquake

Abstract

This work is focused on the failure modes and control strategies of a trial designed super long-span cable-stayed bridge (Abbr. CSB) with a main span of 1400 m under various seismic intensities, exploring the key characteristic of the failure modes of super high tower. Then several control strategies, such as the use of conventional viscous fluid dampers (Abbr. VFDs) and a new combination strategy comprising sacrificial inelastic links and conventional VFDs, are presented for the failure modes improvement and the seismic damage mitigation of the CSB under extreme earthquake (PGA = 1.0 g). It is found that the super high tower experiences an unexpected failure mode with double plastic hinges that shows a new characteristic on the tower failure in the transverse direction, which is different from that of the short- and medium-span cable-stayed bridge during earthquake excitation. Whereas the piers show a typical and expected flexural failure mode with only one plastic hinge in the transverse direction. Although conventional control strategies using the optimal VFDs can help to significantly reduce the seismic damage of the CSB, they cannot entirely make the tower satisfy seismic control targets. It is also observed that the new combination strategy can successfully improve the failure mode and seismic damage of the CSB that satisfies seismic control targets, the effects of proposed combination strategy on the CSB are superior to those of the convention control strategy with the optimal VFDs.