Usefulness of ambient-vibration measurements for seismic assessment of existing structures

A large number of buildings in regions with low to medium seismic hazard have been designed without considering earthquake actions. Retrofitting of all buildings that fail to meet modern code requirements is economically, technically and environmentally unsustainable. Decision-making regarding retrofitting necessity and prioritization is complex. Ambient vibrations are non-destructive and easy to measure, and thus an attractive data source. However, ambient vibrations have very low amplitudes, which potentially lead to sensitivity to testing conditions and stiffness contributions from non-structural elements. Seismic assessment necessitates non-linear behavior extrapolation from linear measurements, which results in biased model predictions. Error-domain model falsification is a data-interpretation methodology that is robust to multi-source uncertainties with unknown and changing correlation values. In this contribution, static non-linear behavior predictions of an existing building in Lausanne, Switzerland, are presented. Ambient-vibration data has been gathered under changing conditions: from undamaged in-service to gradual removal of non-structural elements. Low sensitivity to non-structural elements are found. A numerical model based on the applied-element method is generated and shows potential utility of linear measurements for decision-making using non-linear models involving EDMF under uncertain conditions.