Advanced Negative Stiffness Absorbers for the Seismic Protection of Structures

The KDamper is a novel passive vibration absorption concept, based essentially on the optimal combination of appropriate stiffness elements, which include a negative stiffness element. In this paper, the implementation of the KDamper as a seismic Absorption Base (KDAB) is considered. The paper proceeds to the assessment of the performance of the KDamper as seismic absorption base in a typical flexible 5-storey concrete building structure with a fundamental period of 0.5 sec. The structure is excited by artificial accelerograms, generated to be compatible with the highly demanding Eurocode 8 case C with a PGA of 0.36g, and by real earthquake records. The performance of the KDAB is compared not only to the original structure but also to the cases of conventional and highly damped base isolation systems, as well as the case of a Tuned Inerter Damper (TID). Alternative options for the selection of the KDamper natural frequency are considered, leading to two limit cases. In the first case, the nominal KDamper frequency is selected equal to the low frequency of a conventional base isolation system, resulting in a drastic improvement of the overall structural performance. However, another interesting option is revealed, which foresees the implementation of the KDAB with a nominal frequency much higher than that of the base isolation system. This choice leads to a drastic reduction of the relative base displacement, in the order of few centimeters, combined with acceptable structural performance with respect to drift and absolute acceleration. As a consequence, the KDamper can be implemented as "stiff seismic absorption base", overcoming the disadvantages of the conventional base isolation systems, and thus leading towards alternative seismic protection technologies.