OPTIMAL DESIGN OF ADVANCED NEGATIVE STIFFNESS ABSORBERS

摘要

Throughout the last decades, seismic isolation of structures has attracted the attention of civil engineers and scientists. Research around this field has progressed tremendously, starting from the use of simple elastomeric bearings for the decoupling of the superstructure from the foundation and moving towards the invention of more complex devices (characteristic examples being the Tuned Mass Dampers - TMDs or the Quasi-Zero Stiffness oscillators -QZSs) aiming to enhance structural dynamic behavior. In this paper, an extension of the KDamper (EKD) concept is proposed, for implementation as a seismic base absorber. The complexity of the EKD renders the conventional minmax (H∞) approach ineffective. For this reason, a constrained optimization problem is proposed for the selection of the optimal system parameters. The EKD is designed according to seismic design codes and the constraints and limitations of the EKD components are evaluated based on engineering criteria. A database of artificial accelerograms, compatible with the EC8 response spectra is generated. Sensitivity analysis is performed, and the effect of detuning is observed.Based on a comparison with a conventional base isolated system, the EKD manages to retain the structure absolute acceleration at acceptable levels, while the structure relative displacement is drastically reduced, in the order of a few centimeters, rendering the implementation of the extended KDamper feasible using conventional structural elements, without the need for special types of bearing. Thus, EKD can be considered a possible retrofitting option for seismic protection.