Proceedings home preface contents authors keywords copyright reference ©2012 Civil-Comp Ltd				Paper 196 On the Contribution of Experimental Data to the Reduction of the Uncertainty of Fragility Curves M. Perrault and P. Gueguen Institute of Earth Sciences, University Grenoble I, CNRS, IRD, IFSTTAR, Grenoble, France Keywords: ambient vibration, modal parameters, seismic vulnerability. full paper (pdf) - reference Ambient vibrations in buildings are of increasing interest for applications in mechanical engineering, civil engineering and earthquake engineering. For example, the elastic fundamental frequency and damping ratio are two key-parameters for simplified seismic design and vulnerability assessment methods. Empirical relationships exist in codes to estimate this frequency and damping but experimental data could be used to improve them, by accounting for national features of building design and, above all, by considering corresponding uncertainties. With advances in data acquisition systems (for example the numbers of measurement points, continuous recording and low-noise instruments) as well as advances in signal processing algorithms, further and better studies can be conducted on civil engineering structures for evaluating their modal parameters and their physical properties, with a greater level of confidence. Moreover, permanent instrumentation also provides earthquake data helping in the improvement of the building response for the case of a severe event. This paper shows how the experimental data, obtained from temporary or permanent instrumentation, can be used for adjusting behaviour models, for each class of structure, for the vulnerability assessment by the monitoring of the wandering effect of the elastic parameters on the fragility curves and their uncertainties.