An investigation of a rocking-sliding block

The short end of a rigid rectangular block with a 2:1 aspect ratio is placed on a flat horizontal surface. The surface exhibits a horizontal harmonic motion, and two-dimensional motions of the block are investigated numerically and experimentally. A variety of modes of behavior are possible, and, when viewed from the side, attention is focused on (a) rocking of the block about either bottom comer or (b) sliding while rocking about one of those comers. Different periodic or erratic rocking-sliding responses are observed, with overturning being one of the possible outcomes. This system has relevance to a number of practical applications, especially in the context of earthquake engineering. The experiment consists of two aluminum blocks separated by a heavy steel cylinder. It is mounted on a shake table that oscillates harmonically in the horizontal direction. Data are acquired using image video processing with a number of targets mounted on the block face. Two guides are used to ensure that the motion remains in the vertical plane. Reasonable qualitative agreement between simulations and experimental data is achieved, especially when viewed within the context of highly nonlinear systems and their inherent sensitivity. This work may be considered as an extension to our previous work (Fielder et al., 1997), with the addition of sliding being the major new ingredient.