Development and Spectral Analysis of an Advanced Control Law for Semi-Active Resetable Devices
Passive energy dissipation has advantages such as low cost, easily predictable response, and ease of implementation, which are offset by difficulty tuning or designing devices for optimum behaviour over a range of inputs and responses. Semiactive systems offer customised response and provide a control input that adapts to structural response without excessive energy input. Specific control laws can simultaneously reduce displacement and total base-shear transmitted to the foundation – a unique semi-active capability. These significant advantages can be offset by the limited energy dissipation that can arise as a result. This research focuses on a more effective resetable device control law called the “diamond control law,” for its unique semi-actively enabled device hysteresis loop, which maximises energy dissipation while simultaneously minimising the impact on base shear forces. It achieves this affect by controlling the release of stored energy in the resetable device - smart dissipation in place of maximum or instantaneous uncontrolled release typically used in such devices. A spectral analysis shows that this new approach enables a decrease of 30-40% for both displacement and structural force, which is equivalent to 15- 20% critical viscous damping for an uncontrolled base structure. The total base shear is also decreased by 40%, which has significant potential benefits for retrofit applications. This level of displacement and base shear reductions was not available (in combination) from prior resetable device control approaches, nor from any passive device or system, and thus represents a significant expansion of the design space and capability for seismic energy dissipation.