1.1 General

Modern structures are now built with high-quality materials and with a high utilization of material strengths. This results in larger spans and increasingly slender constructions, reducing the proportion of self-weight in the total load, which is often assumed to be static. The smaller weight and greater slenderness often lead to an increased susceptibility to vibrations in the structures. Recently, there have been more cases where buildings are excited into disturbing or even harmful vibrations by people. Such vibrations particularly affect pedestrian bridges and gymnasiums. It is not uncommon for the vibrations to be so strong that renovation is necessary. Humans have a very good perception of vibrations of all kinds and can feel disturbed even by relatively minor vibrations.