Rocking spectrum intensity measures for seismic assessment of rocking rigid blocks

In this study two novel spectral ground motion intensity measures (IMs) are presented. The proposed IMs are calculated throughout the rocking rotational and the angular velocity spectra which are illustrated as 3D surface graphs, with the slenderness α and the period parameter T, the two horizontal axes. Thus, the IMs are defined as the volume under the spectra, evaluated throughout integration. The proposed IMs are intended to have a strong correlation with the rocking response of free standing blocks. Several rocking rigid blocks subjected to multiple ground motion records are assumed in order to identify the capability of the IMs to predict the rocking response concerning the variability of the block dimensions. The selection of the dimensions was made in order to correspond to slender rocking structures such as electrical equipment, ancient monolithic columns and bridges piers. The evaluation of the IMs was also made by examining characteristics such as efficiency, proficiency and sufficiency. Furthermore, the performance of the proposed IMs are compared with the performance of other well-known ground motion parameters to highlight the adequacy of the former in predicting the rocking seismic response.