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Experimental Shake Table Testing of an Adaptive Passive Negative Stiffness Device within a Highway Bridge Model

The implementation of a mechanical negative stiffness device (NSD) within a reduced-scale highway bridge model and its performance under seismic loading conditions is evaluated via shaking table tests. Four different isolation system configurations are considered: isolated bridge (IB), IB with viscous dampers, IB with NSDs, and IB with viscous dampers and NSDs. In addition, two bridge pier configurations were considered: one with flexible piers (mimicking a middle span of a multi-span bridge) and one with braced piers (mimicking a single span bridge supported on abutments). The main feature of the NSD is a large pre-compressed spring, which can push the structure away from its initial undeformed position and thus induce negative stiffness behavior. The experimental results clearly demonstrate the effectiveness of the NSDs in limiting the seismic response of the bridge and provide validation of numerical simulation results wherein numerical models of the bridge model components were calibrated via system identification testing.