Robust hybrid control of a seismically excited cable-stayed bridge

Abstract

A cable-stayed bridge has become a popular type of bridge throughout the world because of its aesthetic shape, structural efficiency, and economical construction. However, such a structure may be vulnerable to dynamic loads such as earthquakes and strong winds due to its flexibility, low structural damping, and so on. Structural control systems such as passive, active, semiactive, or combinations thereof, can provide an efficient means for seismic protection of cable-stayed bridges. This dissertation proposes an efficient robust hybrid control system for a seismically excited cable-stayed bridge. The common usage of the term “hybrid control” implies the combined use of passive and active/semiactive control devices. Because multiple control devices are operating, hybrid control systems can alleviate some of the restrictions and limitations that exist when each control device is acting alone. The proposed hybrid control systems are based on the passive control devices combined with active or semiactive control devices. Lead rubber bearings are used as passive control devices to reduce the earthquake-induced forces in the bridge and to increase the control system robustness by the inherent reliability of lead rubber bearings. Hydraulic actuators or magnetorheological fluid dampers are used as additional active or semiactive devices to further reduce the responses, especially deck displacements (i.e., deformations of lead rubber bearings) and to increase the control system robustness by appropriate control algorithms. To verify the control performances of the proposed hybrid control systems, a set of numerical simulations is performed and the results are compared to those of passive, active, and semiactive control systems. There are many differences between a real bridge and alternate mathematical model and many uncertainties on structures, control devices, input excitations, and so on. For example, the earthquake excitations are highly uncertain with respect to m...