Experimental Study On Active Control Of Cable-stayed Bridge Under Construction

A cable-stayed bridge under construction has low structural damping and is notas stable as the completed structure. The system is easy to vibrate due to windexcitation, which may affect the comfort of workers. If gust and/or earthquake occurlarge forces may be caused, which may even lead to safety problems of structure andconstruction devices. Control countermeasure, such as the installation of energydissipating devices, is needed. For cable-stayed bridge is a flexible and spacialstructure which has complicated static and dynamical characteristics, active control isa strong candidate for the mitigation of structural vibration.Structural active control, which is of powerful capacity to reduce structuralvibration response due to wind, earthquake or other dynamic excitations, is a recentresearch forcus among the community of structural engineering. In this research, thegeneral procedure and key issues on adopting an active control device, the activemass damper (AMD), for vibration control of buildings and bridges are studied.To find efficient and reliable control algorithms for AMD-based active control, acomparative study is conducted firstly on a benchmark 2-floor frame, which isequiped with two electro servo AMD cart on each floor. The state equations arededuced using Lagrangian approach. The controllers are then designed using poleallocation, LQR, LQG and H_∞algorithms under the support of Kalman Bucy filterwith acceleration feedback. A simulation study for the structure under seismic iscarried out in Matlab. The best controller, the LQG controller, from simulationanalysis is applied to an experiment. The results confirm the electro servo AMD carts'efficiency and the robustness of the LQG controller on controlling the vibration ofthe structure.After successful application of the AMD system on vibration control of framebuilding, it is further adopted to control the horizontal vibration of the bridge deck ofa cable-support bridge. Taking the simplified model of the Third Nanjing YangtzeRiver Bridge under construction as an example, this research demos the generalprocedure for active control of cable-stayed bridges. Theoretical derivation andnumerical case study show that multiply control devices should be placed along the structure to achieve an acceptable control performance for a structure of modes withrepeated frequency.The case studies on the frame building structure and the simplified cable-stayedbridge structure verified that the AMD-based active control is feasible and efficientfor reducing dynamical responses of complex structural system, such as thecable-stayed bridge under construction.