Re-shaping hysteretic behaviour using resetable devices to customise structural response and forces

Abstract

Semi-active dampers have significant capability to reduce wind and seismic structural response. A novel resetable device with independent valve control laws that enable semi-active re-shaping of the overall structural hysteretic behaviour has been recently developed and validated. Three methods of re-shaping structural hysteretic dynamics are statistically analysed in a performance-based seismic design context. Response reduction factors from the uncontrolled case are obtained across a spectrum of structural natural periods for displacement response, structural force, and total base shear. Overall results indicate that reduction factors are suite (near-field versus far-field) invariant. Resisting all motion and resetting at zero velocity adds damping in all four quadrants and showed 40-60% reductions in the structural force and displacement at the cost of a 20-60% increase in total base-shear. Resisting only motion away from equilibrium adds damping in quadrants I and 3, and gave reductions of 20-40%, with a 20-50% increase in total base-shear. However, only resisting motion towards equilibrium added damping in quadrants 2 and 4 only,, for which the structural responses and total base-shear were reduced 20-40%. The reductions in both response and base-shear indicate the appeal of this unique, semi-active hysteresis sculpting approach for seismic retrofit applications largely due to the reduction of the force and overturning demands on the foundation system