The concept of apparent weakening by adding true negative stiffness to a structure has been previously introduced by the authors in order to reduce simultaneously drifts, accelerations and displacements in a structure, without yielding or permanent deformation in the main system. A novel Negative Stiffness Device (NSD) that generates true negative stiffness has been developed, built and tested, and has been previously described by the authors in terms of operation and analytical and numerical modeling. This paper presents results that represent proof-of-concept for weakening with the use of the NSD based on the shake table testing of a 3-story seismically isolated structure, equipped with these devices and viscous dampers. The NSD is shown to have a significant effect on the superstructure response by reducing floor accelerations, story drift and the base shear, and upon the addition of dampers also results in a reduction in isolator displacements. Moreover, this paper provides validation of the analytical models that were previously developed by comparison of analytical and experimental results.
Published in the 3rd ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering. M. Papadrakakis, M. Fragiadakis, V. Plevris (eds.) Corfu, Greece, 25–28 May 2011.
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