Seismic Vulnerability assessment using ambient vibrations : method and validation

International audienceSeismic vulnerability in wide areas is usually assessed in the basis of inventories of structural parameters of the building stock, especially in high hazard countries like USA or Italy. France is a country with moderate seismicity so that it requires lower-cost methods. Ambient vibrations analyses seem to be an alternative way to determine the vulnerability of buildings. The modal parameters we extract from these recordings give us a 1D model for each class of building found in the study area. We then study the response of these models to realistic seismic excitations (scenarios) including site effects in order to determine a threshold acceleration sustained by this class of building which we interpret as a vulnerability index. The distribution of the classes in the city will lead to a vulnerability map. In order to validate this method, we compare the modal parameters of a building in Grenoble (France) determined under ambient noise and during a stronger excitation: the demolition of a nearby bridge. A statistical study of recordings using time windowing gives uncertainties and leads us to conclude that the modal parameters are equal