University of Auckland Centre for Earthquake Engineering Research

Mechanics of rocking structures subjected to ground motions

Results acquired from this research were used to verify hypotheses on how a rocking motion affects structures in an earthquake.

Historically, documented cases exist on how fortuitous rocking has aided the survival of seemingly unstable structures during large earthquakes. Researchers have attributed this to the lateral softening and energy dissipating properties of a stable rocking motion. More recently, rocking isolation has been favoured and applied for seismic retrofit project worldwide. The most notable example is the recent seismic retrofit project for the Lion's Gate Bridge in Vancouver, whereby essentially the holding down bolts for the structure were remove to increase its seismic capacity.

Scientist and engineers have since found that rocking in addition to having simple intuitive response in fact possess a range of complex behaviours, more akin to a chaotic nonlinear dynamic system. Subsequently, the confident prediction of the time dependent dynamic response of a rocking object remains unattainable and untested.

In light of this, this research project further developed the underlying theoretical background of natural and newly emerging hybrid rocking mechanisms as it is applied to structures for seismic protection. Dynamic full scale testing was conducted on a rocking structure and the experimental results subsequently used to verify research hypotheses.