Specialist know-how: Mitigation Measures for Vibration-Prone Structures
Long-span, lightweight structures in particular are susceptible to excitation as a result of loads exerted by people, machines, traffic, wind and earthquakes. This can adversely affect their serviceability and, in extreme cases, place the loadbearing capability of these structures at risk. Vibration problems in structures occur when the frequency of the excitation is close to the structure's natural frequencies and it has very little damping. For example, vertical vibrations induced by walking or running people have excitation frequencies of 1.6 to 3.5 Hz, hopping and dancing people 1.5 to 3.4 Hz.1 Lightweight footbridges, concert hall stages and long-span floors of residential and office buildings are susceptible to this type of excitation. The relevant frequencies of vibrations caused by rail transport vehicles are between 10 and 50 Hz, which covers the typical natural frequencies of reinforced concrete and timber floors. Earthquakes have the largest frequency content - depending on the ground stiffness - of between 1.3 and 20 Hz. Buildings up to 40 m tall in particular are susceptible to this horizontal excitation.
