Dynamic properties of buildings evaluated through ambient noise measurements

Abstract

It is well known that the damage level and its distribution during an earthquake is due to the combined effects of seismic hazard in the investigated area, the features of the local site response, based on the near–surface and subsurface ground conditions, as well as on the dynamic features of the erected buildings. The extent of building dam- age and its distribution is indeed tightly linked to the combined effect of local site response and the dynamic features of the human-made structures. The dynamic properties of a building are usually described through its natural frequency (or period T) and the damping ratio (ζ ), the latter representing the energy loss of an oscillating system. The damping ratio is important in seismic design since it allows to evaluate the ability of a structure to dissipate the vibration energy during an earthquake. Such energy causes a structure to have the highest amplitude of response at its fundamental period, which depends on the structure’s mass and stiffness. The knowledge of damping level and fundamental period of the building is therefore particularly important for estimating the seismic base shear force F in designing earthquake resistant structures.