Theme Lecture – Negative Stiffness Elements in Seismic Isolation of Bridges
Throughout the last decades, seismic isolation of bridge structures has attracted the attention of civil engineers and scientists, since bridges belong to the category of structures whose functionality needs to be preserved after an earthquake event. Research around this field has progressed tremendously, starting from the use of simple elastomeric bearings for the decoupling of the bridge’s deck from the abutments 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 context, the implementation of novel passive seismic isolation devices incorporating negative stiffness elements to bridge structures is introduced and proposed in this effort. The design of these devices follows the scope of a general vibration isolation and damping concept, entitled KDamper concept based on Antoniadis et al. (2016). The realization of negative stiffness elements includes two different approaches regarding the type of bridge structure considered, namely pre-stressed springs in proper geometric arrangements for bridges with solid-sectioned piers and a specialized inverted pendulum mechanism for bridges with hollow-sectioned piers. The proposed systems are compared to the initial undamped models as well as with similar structures employing other seismic isolation techniques. Comparative results prove the efficiency of the proposed KDamper system.