Earthquake Rocking Response of Rigid Bodies

Using a computer program, the rocking and overturning response of rectangular blocks of various sizes and aspect ratios is studied under several strong motion earthquakes. The effect of coefficient of restitution and of vertically prestressing the blocks to the floor is also studied. This investigation was undertaken primarily to study the response of solid concrete block stacks used as radiation shields in particle accelerator laboratories. Results from this study indicate that rocking should be prevented in such systems on account of the possibility of overturning once rocking commences, unless a tie-down design is used. The paper also points out the sensitivity of overturning to small changes in base geometry and coefficient of restitution as well as to the form of the ground motion. This suggests that it may be difficult to use data from observations on standing and overturned rigid bodies after an earthquake to provide much useful information on the intensity of ground motion.