Displacement based analysis and design of rocking bridges

Abstract

The response of a rigid rocking block is traditionally described by its tilt angle. This is a correct description, but this paper suggests that describing rocking via displacements is more meaningful, because it uncovers that two geometrically similar blocks of different size will experience the same top displacement, provided that they are not close to overturn. The above is illustrated for both analytical pulse excitations and for recorded ground motions. Thus the displacement demand of a ground motion on a rocking block is only a function of its slenderness; not of its size. This reduces the dimensionality of the problem and allows for the construction of size-independent rocking demand spectra.