AbstractComprehensive studies of rigid structure responses to seismic ground excitations have been reported. It was found that the rocking and sliding response of a rigid structure is highly nonlinear. The structure stability depends on the structure slenderness, as well as the ground motion amplitude, frequency and duration. Compared to an earthquake ground motion, ground shock induced by underground or surface explosion has very large amplitude, high frequency and short duration. Moreover, vertical component of a ground shock may be substantially larger than the gravitational acceleration g. This will cause the unanchored rigid structure jump or fly into air. Therefore, the responses and stability regions of a rigid structure to blast induced ground shock will be very different from those under seismic ground motions. No study of rigid structure response to ground shock of amplitude more than 1.0g can be found in the literature. As there might be many rigid structures such as computers, document shelfs, and other important equipments in a building or a military command center close to an explosion center, understanding rigid structure response to ground shock is essential for protection of such equipments. In this study, theoretical derivation and numerical prediction of rigid structure response to ground shock are carried out. Numerical results of stability regions of rigid structures to ground shock are derived. Particular attentions are paid to the case when the vertical ground shock is more than 1.0g and the rigid structure flies into the air. Results are compared to those obtained with earthquake ground motions. Discussions on the rigid structure stability to earthquake motion and ground shock are made.