Hybrid seismic protection of cable-stayed bridges

This paper proposes a hybrid control strategy combining passive and semi-active control systems for seismic protection of cable-stayed bridges. The efficacy of this control strategy is verified by examining the ASCE first-generation benchmark problem for a seismically excited cable-stayed bridge, which employs a three-dimensional linearized evaluation bridge model as a testbed structure. Herein, conventional lead-rubber bearings are introduced as base isolation devices, and semi-active dampers (e.g., variable orifice damper, controllable fluid damper, etc.) are considered as supplemental damping devices. For the semi-active dampers, a clipped-optimal control algorithm, shown to perform well in previous studies involving controllable dampers, is considered. Because the semi-active damper is a controllable energy-dissipation device that cannot add mechanical energy to the structural system, the proposed hybrid control strategy is fail-safe in that the bounded-input, bounded-output stability of the controlled structure is guaranteed. Numerical simulation results show that the performance of the proposed hybrid control strategy is quite effective in protecting seismically excited cable-stayed bridges.