ABSTRACT
Herein lies the solution to the problem of a description of damping behaviour, because the amount of 'stuckness' is well defined in the field of fracture mechanics. The longer the boundary between two elements, the lower the force necessary to produce relative motion. With two small elements requiring a large force to separate them, we are in the ambit of intermolecular forces. Whilst at first sight this may not seem important to structural engineers, in practice the opposite is the case. Cracking in the material of the structure starts at a molecular level, and the initiation of cracking is now seen to be the key to the start of relative motion between elements in a structure. The forces that initiate cracking in a structure, or that cause relative motion between large elements (such as beams and columns), are shear forces themselves caused by the dynamic motion of the structure. This is another unifying theme, because the same mechanism that leads to a degradation of stiffness of a structure also causes there to be a greater amount of damping.
