Conventionally designed structural frame systems develop significant inelastic deformations under strong earthquakes, leading to inelastic hysteretic behavior, stiffness and strength degradation, increased interstory drifts, and damage with residual drift. Passive seismic protection systems in the form of supplemental damping devices have emerged as an effective approach for reducing response and limiting damage by shifting the inelastic energy dissipation from the framing system to the dampers. However, such dampers do not generally provide self-centering stiffness capability or counter stiffness degradation. Recent investigations have shown that a combination of adaptive stiffness and damping (ASD) devices can provide substantial response modification, particularly during near-fault pulse-type earthquakes. ASD devices offer structural response modification capability by optimally varying the restoring forces (stiffness) linked to the frequencies of vibration and dissipative forces (damping) that govern the behavior of a structural dynamic system. To date, adaptive stiffness systems have received relatively little attention as compared to supplemental damping systems and thus represent a significant gap in earthquake engineering. Hence, development of new ASD devices is necessary to shift the energy dissipation and associated stiffness variations from the structural system to the ASD devices to reduce damage in frames, eliminate residual interstory drift, and provide self-centering capability.
ASD devices exhibit strong rate-dependence and thus they need to be tested at high velocities such as those that are induced by near-fault pulse-type ground motions. Furthermore, to fully validate their behavior, large scale model tests of the devices within building frames and bridges is needed. Thus dynamic large scale testing methods are required. Such testing capabilities are available through the UB-NEES facility. Specifically, the UB-NEES facility offers the capability to experimentally evaluate ASD systems in large-scale multistory building and bridge systems using multiple shake tables. Multiple support 6DOF excitations induced by multiple shaking tables is feasible only at UB-NEES. Such testing of scaled building and bridge models with multiple support excitations of devices would not be possible without facilities at UB-NEES.