COIMPARISON OF THE DYNAMIC PARAMETERS EXTRACTED FROM WEAK, MODERATE AND STRONG MOTION RECORDED IN BUILDINGS.

Ambient vibration analysis is proposed as an alternative way to inspect buildings before or after an earthquake. This fast and low-cost method is well-adapted to large-scale studies for which a large amount of buildings has to be checked. One of the most common critics usually done on the use of ambient vibrations in structures is the very low level of vibrations. Because of the low amplitude range of the ambient vibration (PGA<10-5g), dynamic characteristics obtained from weak-motion are generally expected to be significantly different from those obtained using strong-motion (PGA>0.1g). The objective of this paper is to present a comparison of the structural dynamic characteristics deduced from strong, moderate and weak motion recordings for a set of twelve Californian buildings and four European buildings. The present study differs from numerous previous investigations in two aspects: (a) the number of compared building is larger; and (b) for two buildings, more than 10 earthquakes records are available, which allows to investigate the dependence of dynamic characteristics with shaking intensity