Rocking of rigid non-symmetric blocks standing on a horizontally-moving compliant base

Rocking of a non-symmetric block on a compliant horizontally-moving base is explored for the first time in this paper through a combination of analytical, numerical and experimental approaches. A compliant base model is proposed, which is shown to have good overall accuracy, in particular predicting when rocking will be initiated. The proposed model predicts a significantly lower rocking threshold, which is much more sensitive to the eccentricity of the centre of mass, in comparison with the threshold determined assuming the base is rigid. The proposed model predicts that a highly non-symmetrical block, with its centre of mass outside the middle third of its base, will have uplifted even when it is at rest and no horizontal excitation is applied. The proposed model also predicts lower overturning thresholds, which is because the static overturning angles reduce when the compliance of the base is accounted for. The proposed compliant base model provides an accurate tool suitable for the design of base isolation systems for the seismic protection of freestanding museum artefacts or mechanical equipment, as evidenced by the extensive numerical and experimental test results presented in this paper.