Abstract:
A series of free vibration tests has been conducted on a free standing single degree of freedom structure with a range of elastic natural frequencies; the tests were conducted over a rigid concrete floor and over typical Auckland soil. A typical response was obtained when the structure was rocked over the concrete floor. The response fitted Housner’s simple rocking model, however it further emphasised discrepancies in the calculation of the damping factors. Intriguingly, the experimental result showed that the amount of radiation damping, measured as the apparent co-efficient of restitution, is relatively constant irrespective of the structure’s geometry contradicting the simple rocking models. The results showed that when the structure rocked on insitu ground, the dynamic behaviour was greatly modified. The time history response demonstrated a change of principle damping scheme from radiation to viscous. The response over the elastic medium failed to correlate with Housner’s model due to increased viscous damping and an elongation in the rocking period for a given amplitude was observed.
