Predictive Capabilities of the Alpha Method: Shaking Table Tests and Field Data Verification

This paper verifies the accuracy and effectiveness of the “alpha” method for maximum rotational response prediction as applied to a wide range of eccentric systems and earthquake excitations. The verification is carried out either through extensive numerical investigations, through shaking table tests and through the analysis of actual responses of two Californian base isolated structures subjected to some of the most recent earthquakes occurred in their regions. These studies showed the applicability of the proposed “alpha” method which is found to be sufficiently accurate (for engineering purposes) and robust over a wide range of eccentric system parameter values and dynamic excitations. These successful verification results also confirm that the dimensionless structural parameter “alpha” used in the proposed simplified method can alone be used to quantify the pre-disposition of a given eccentric system in developing a rotational response under earthquake excitations.