Rocking of a Rigid Block on a Curved Foundation

Principal Investigators: Jonas Bachmann, Dr. Michalis Vassiliou, Prof. Dr. Bozidar Stojadinovic

Severe but rare earthquake have severe socioeconomic consequences. Current seismic codes prevent collapse, but inelastic response and damage of the structure is accepted. The costs associated with repairs of this kind of damages can be huge. Sometimes repair is not even an option due to the large residual deformations: in this case damaged buildings are demolished and rebuilt.

In the context of using rocking as a structure response modification and damage mitigation mechanism, this research project aims to investigate the dynamic response of rolling-then-rocking structural systems. These systems work as mechanical fuses to limit the seismic forces transmitted to the structure. Moreover, structures employing such systems are resilient: after an earthquake they re-center to their original position without damage. The dynamic response of the rolling-then-rocking systems is controlled by the geometric characteristics of the contact surface with the foundation. The principal idea is to engineer the post-uplift stiffness of such rocking systems by extending their flat base using concave surfaces, thus introducing a rolling phase in between the at-rest state and the rocking motion phase.

Curving the outer part of the base introduces one additional design parameter that can be used to optimize the response of the block so that the system is at least as stable as the same-size flat-based one (for extremely rare earthquakes), while decreasing the bending moment demand for more frequent earthquakes.