ABSTRACT

The largest cracks that participate in energy dissipation in a structure seem to be in the region of 20 mm long. As shear forces increase, more and more cracks are induced to increase their length as they are torn. This situation is described in detail in the study of fracture mechanics. As the amplitude of motion increases, smaller and smaller cracks in the material of the structure are mobilized until an effective limit is reached at approximately 100,um. Since there are large numbers of potential cracks, and elongating cracks within the material of a completed structure, then there is great potential for energy dissipation. This region of motion is the one in which damping increases with increasing amplitude of motion of the structure.