Nonlinear vibration characteristics of stayed cables under non-uniform seismic input considering bridge-cable interaction

Large-amplitude nonlinear dynamic responses of stay cables induced by local vibrations and complex cable-girder-tower interaction during an earthquake can adversely affect the overall performance of cable-stayed bridges. For super-long-span cable-stayed bridges, the spatial variability of ground motions further affect the structural seismic response. Although spatially varying seismic excitation and nonlinear cable-bridge interaction have each been investigated, their coupled effects on long cable-stayed bridges remain insufficiently quantified. Taking a real kilometer-scale twin-tower cable-stayed bridge as an example, the advanced multi-element cable system (MECS) is adopted to establish a macroscale finite element model of a cable-stayed bridge on the OpenSees platform. Considering selected non-uniform seismic excitations with varying wave passage angles and travelling wave velocities, the complex nonlinear vibration characteristics of the cables and the corresponding impact on the seismic responses of the bridge are analyzed. The comparison of results from the OECS and MECS models reveals the following. (i) The MECS model can capture large-amplitude forced resonance in cables, indicating that cable nonlinear vibration lead to energy redistribution under drastic earthquakes similar to the effect of tuned-mass dampers. (ii) The differences between the MECS and OECS results are more profound under non-uniform seismic excitations as compared to those under uniform seismic excitations, which may amount to 20%-30%. (iii) The cable resonance behavior of the bridge is relatively severer when the seismic wave passage angle lies between 45° and 90° or when the travelling wave velocity is around 500 m/s. In-depth seismic response analysis utilizing advanced MECS technique is highly recommended for accurate modelling and assessment of cable-stayed bridges susceptible to seismic bridge-cable interaction.