ADVANCED NEGATIVE STIFFNESS VIBRATION ABSORBER COUPLED WITH SOIL-STRUCTURE INTERACTION FOR SEISMIC PROTECTION OF BUILDINGS

摘要

Throughout the past decades, seismic isolation of structures has been studied rigorously as an approach to reduce seismic demand and mitigate structural damage. Research in this field has progressed significantly, starting from the use of simple elastomeric bearings for the decoupling of the superstructure from the base, to more complex devices that incorporate the use of an additional oscillating mass and negative stiffness elements. Characteristic examples of these devices are the Tuned Mass Damper (TMD) and the Quasi-Zero oscillators (QZSs). The KDamper is a novel passive vibration absorption concept, based essentially on the optimal combination of appropriate stiffness and mass elements, which include a negative stiffness element. The concept can be implemented using a system of prestressed elements in order to obtain the negative stiffness effects and might prove to achieve a significant advantage for seismic retrofitting. In this paper, the extended KDamper system is placed at the ground level and the soil-structure interaction (SSI) between the building foundations and superstructure is utilized as a means to effectively transfer the dynamic forces of the KDamper to the building and to distribute the required displacements between the structural elements and foundation, thus leading to absorption of the vibration energy. The configuration of the KDamper properties and tuning of its stiffness elements are studied herein. The effectiveness of the KDamper is subsequently investigated in view of the performance of a 4-storey building. A series of artificial accelerograms and real earthquake time histories are used as excitation. Results indicate the beneficial role of SSI on the reduction of the spectral acceleration and displacements, hence placing the concept as a compelling alternative to existing seismic protection technologies.