Dimensional Analysis of Negative Stiffness Bilinear Systems under Pulse Like Excitations
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Date
2021
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Conference Paper
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yes
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Abstract
Rocking has been proposed as a seismic design strategy for bridges and buildings, as rocking structures experience minimal residual displacements. In order to provide redundancy to rocking systems and to control their displacements, researchers in New Zealand and the USA have proposed to use unbonded restraining tendons within the rocking elements. In parallel, in the former USSR and currently in former USSR countries, a rocking solution has been used, where the rocking elements are extended with curved wedges to increase their displacement capacity, without increasing the design forces of the superstructure.
In terms of their pushover curves, the above two systems are similar, as they present an initial relatively stiff branch followed by a linear branch that can be of positive or negative stiffness, depending on the stiffness of the tendon or the curvature of the curved wedge. Unloading follows the same branch without any hysteretic energy dissipation (unless the structure is equipped with extra energy dissipaters). Energy dissipation happens instantaneously during impact. Opting for positive stiffness is the current state of the practice. However, a negative stiffness design would lead to a smaller design moment for both the superstructure and the foundation, potentially not requiring piles.
Therefore, there is a need to better understand the dynamics of negative stiffness systems with instantaneous damping. This paper studies the general bilinear negative stiffness oscillator. It uses dimensional analysis to determine the nondimensional quantities that better describe the problem, and presents response spectra for analytical pulses. It shows that for negative stiffness systems, the addition of flexible tendons or large curvature wedges increases the displacement capacity of the system, while it keeps the displacement demand almost constant. Moreover, it discusses the influence of the characteristics of the first branch of the bilinear curve on the overall response of the system.
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published
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Book title
Proceedings of the Seventeenth World Conference on Earthquake Engineering Japan 2021
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Publisher
National Information Center of Earthquake Engineering
Event
17th World Conference on Earthquake Engineering (17WCEE 2020-21)
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Subject
Negative stiffness systems; Dimensional analysis; Non linear dynamics; Bilinear systems
Organisational unit
09663 - Vassiliou, Michalis (ehemalig) / Vassiliou, Michalis (former)
Notes
Conference postponed due to Corona virus (COVID-19), and rescheduled from September 1318, 2020 to September 27 - October 2, 2021. Conference lecture held on October 2, 2021. Grant ETH 18-10-1.