Spectral analysis and Assessment of a net-zero base-shear energy dissipation approach for seismic energy mitigation

Abstract

Combining passive and semi-active damping has unique benefits that cannot be achieved through other damping techniques alone. Passive high force to volume (HF2V) lead dampers offer high energy dissipation, but have no ability to customise overall response. Semi-active resetable devices offer adaptability and custom hysteresis loops that can reduce both displacement and base shear, but are limited in overall energy dissipation capability. Together, these devices offer a new concept to maximised displacement response reduction, without increasing base shear – a net zero base-shear concept. This paper combines HF2V devices, with design force levels up to 10% of weight, and a resettable device with nominal stiffness of 100% of column stiffness. A spectral analysis is run to size the HF2V device iteratively at each period to achieve maximum reductions in displacement without increasing median base shear. The results show up to 50% reduction in base shear for the low suite, and up to a 40% reduction for the medium and high suites. Towards longer periods, base shear reduction factors tend to 1.0, indicating net-zero base-shear. This situation is never reached below a structural period of 2.5s, where median base-shear reduction factors are less than 1.0, indicating a reduction in base-shear as well as displacement and structural force. Overall, these results are independent of HF2V device scaling, as analyses using ground motion specific mean velocities and 1m/s mean velocity for sizing the device capacity yield closely similar results. Comparisons are also drawn between the performance of the combined damping system to that of the passive and semi-active systems alone.