Effects of Rotational Ground Motions on Floor Acceleration Demands in Reinforced-Concrete Buildings

The influence of rotational ground motions on floor acceleration responses in eight regular reinforced-concrete moment-resisting frame buildings are examined. A total of 4,800 bi-directional and tri-directional time-history analyses were conducted across five seismic demand levels using a suite of far-field earthquake records and simulated rotational ground motions. The results indicate that rotational ground motions can amplify peak floor acceleration and total acceleration at floor edges up to 45% and 121%, respectively, particularly in short-period inelastic buildings. Simplified recommendations are proposed and validated to account for the effects of rotational ground-motion into seismic design of acceleration-sensitive secondary systems in reinforced-concrete buildings located at far-fault sites.