Toppling of Computer‐Type Equipment under Base Excitation

An analysis is given of the statistical and probabilistic properties of the random time at which a piece of essential equipment, such as a computer, may topple under base excitations. The equipment is modeled as a rigid block, and the base accelerations are modeled as white noises in horizontal and vertical directions. The cases of a free‐standing block and an anchored block are both considered. The white‐noise idealization resembles the most intense portion of ground acceleration in a seismic event, which is an acceptable simplification provided that the correlation times of actual base excitations are short compared with the dominant quasi‐periods of the induced rocking motion. It is shown that the presence of vertical excitation about one‐half the level of horizontal excitation may increase the probability of toppling by 30–40%, and that larger blocks are more stable than the smaller ones of the same geometrical proportion. The analysis is also applicable to such objects as monuments, storage tanks, and certain types of tall buildings.