Spectral analysis for a semi‐active–passive net‐zero base‐shear design concept

Abstract

Passive high force-to-volume (HF2V) dampers offer significant displacement reduction and energy dissipation, but cannot customise overall response. Semi-active resettable devices offer adaptive, custom hysteresis loops that reduce displacement and base shear, but have limited dissipation. This paper presents a new, combined concept to maximise displacement reduction without increasing base sheara net-zero base-shear concept.HF2V devices, up to a maximum of 10% structural weight, are combined with fixed stiffness resettable devices. Spectral analyses are run for the three SAC ground motion suites that iteratively size the HF2V device at each structural period to achieve maximum displacement reductions without increasing median base shear. HF2V velocity dependence and the need to scale HF2V capacity to spectral velocity are examined in terms of their impact on the results of these analyses.The net-zero approach reduces base shear by up to 50% and displacements by 30-70% over all ground motions, exceeding reductions obtained by either device separately by 30-50% (relative). The net-zero condition is not reached within the device limits defined, except at relatively long periods (>3.5 s) because of a virtuous circle of reduced displacement from the resettable and HF2V devices outweighing the increased base shear from the HF2V devices alone. These results are independent of HF2V device scaling, design and velocity dependence. The overall net-zero concept offers a significant advantage in a combination that cannot be achieved by passive or semi-active solutions alone.primarily to present the net-zero base-shear concept and the unique approach of specifically managing the base-shear demands of the structure. This investigation presents an initial framework for assessing the efficacy of the concept and presents some overall indicative results suitable for use in design and specification.

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Author's reply to discussion on: probabilistic risk analysis of structural impact in seismic events for linear and nonlinear systems

“…Presumably, it could be ascribed to simple structures with one primary degree of freedom. This is accepted in the term ‘earthquake response spectra’ and has been used in various spectral analysis studies ; multidegree‐of‐freedom structures with the same number of degrees of freedom and same basic form; or multidegree‐of‐freedom structures of different types.…”

“…Presumably, it could be ascribed to (i) simple structures with one primary degree of freedom. This is accepted in the term 'earthquake response spectra' [1,2] and has been used in various spectral analysis studies [3][4][5]; (ii) multidegree-of-freedom structures with the same number of degrees of freedom and same basic form; or (iii) multidegree-of-freedom structures of different types. Furthermore, for interbuilding pounding studies, either one or both structures may be analyzed with a range of frequencies or periods for spectral analysis.…”