Control for Multiple Objectives in Different Magnitude Excitations

Linear structural control strategies generally cannot focus on different objectives in different excitations. Yet, this is a goal that has real meaning in many structural control applications. For example, minimizing structural drift is necessary during strong earthquakes to mitigate damage to the structure; however, occupant comfort and the safety of building contents and nonstructural components in the much-more-frequent moderate earthquakes demand reductions in absolute accelerations. Drift and acceleration reduction in different excitations are competing objectives that cannot be achieved with conventional linear strategies. Herein, a control strategy is presented that achieves significant improvements in both serviceability (acceleration mitigation) in weak/moderate excitations and life safety (drift mitigation) in extreme events, all in one general control law. A numerical study of a simple single degree-of-freedom system, using scaled records of several historical earthquakes, controlled with conventional LQR approaches and the proposed control, demonstrates that the proposed control law successfully accomplishes both goals.