New Active and Semi-Active Isolators for Structures Subjected to a Strong Earthquake
In this paper, an optimal control matrix, based on the modified differential equation of Riccati, will be formulated, for the active isolation analysis of structures subjected to earthquakes, and a passive mechanical isolator device which is will be also proposed. The combination of the active and the passive isolators compose a Semi-Active Variable Stiffness and Friction Isolator (SAVSFI) model which proposed for the nonlinear analysis of structures subjected to earthquakes. The active feedback gain is determined in terms of the optimal control matrix for which with the passive device model present indeed, new propositions to reduce actively and semi-actively the effect of earthquakes on the responses of civil engineering structures. Three examples of structures (two buildings and a bridge) have been analyzed for the three uncontrolled, active-controlled and semi-active-controlled cases and subjected to a strong earthquake. The results obtained either displacements or stresses for the active and the semi-active cases, show good and excellent reductions, in comparison with those deducted for the uncontrolled cases. This good reduction of the effect of such strong earthquake would be turns to the good formulation of the optimal active feedback gain computed and to the good passive mechanical model proposed.
Modified Riccati Equation, Nonlinear Quadratic Regulator Method, Active Control, Semi-Active Isolator, Nonlinear Analysis, Seismic Excitations
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