Re-Shaping Hysteresis: Seismic Semi-Active Control Experiments for a 1/5th Scale Structure
Semi-active resetable devices can improve seismic response. Novel 2-4 devices independently control each device chamber to customise structural hysteresis loops to reduce both displacement and base shear demands. Here, 2-4 devices are experimentally validated on a one-fifth scale test structure weighing 35kN with a natural period of 0.6 seconds. Four seismic inputs over a wide range of intensity levels are use in 27 tests. Results for resetable semi-active devices that modify hysteretic behaviour using different control laws are compared to spectral response analyses that predict ~30-50% peak displacement reductions. Fully uncontrolled tests were also done for lower intensity ground motions, along with fail-safe valves-open tests. Results show 25-50% peak displacement reductions compared to the valves open case, depending on the semi-active control law used and matching spectral analysis results. Additionally, a semi-active control law designed to simultaneously reduce base shear reduces it 10-20%. In contrast, 10-20% increases are seen for other approaches, as predicted. Overall, these are the first large-scale tests of this type of novel resetable devices. The results validate prior simulation and spectral analyses, and clearly show the potential. Finally, semi-active methods that re-shape hysteresis to control response and simultaneously limit base shear demand, are experimentally demonstrated for the first time.