The aim of this paper is an empirical estimation of the fundamental period of reinforced concrete buildings and its variation due to structural and non-structural damage. The 2009 L'Aquila earthquake has highlighted the mismatch between experimental data and code provisions value not only for undamaged buildings but also for the damaged ones. The 6 April 2009 L'Aquila earthquake provided the first opportunity in Italy to estimate the fundamental period of reinforced concrete (RC) buildings after a strong seismic sequence. A total of 68 buildings with different characteristics, such as age, height and damage level, have been investigated by performing ambient vibration measurements that provided their fundamental translational period. Four different damage levels were considered according with the definitions by EMS 98 (European Macroseismic Scale), trying to regroup the estimated fundamental periods versus building heights according to damage. The fundamental period of RC buildings estimated for low damage level is equal to the previous relationship obtained in Italy and Europe for undamaged buildings, well below code provisions. When damage levels are higher, the fundamental periods increase, but again with values much lower than those provided by codes. Finally, the authors suggest a possible update of the code formula for the simplified estimation of the fundamental period of vibration for existing RC buildings, taking into account also the inelastic behaviour.

This letter aims at analyzing the potentialities of the ground-based microwave radar interferometry technique for the dynamic characterization of civil infrastructures. This technique has been applied to estimate the fundamental dynamic parameters of the reinforced concrete Musmeci bridge in Basilicata region (southern Italy). The results have been validated by the comparison with the ones obtained applying consolidated techniques using data from accelerometers and tromometers. The good agreement obtained could suggest the joint application of such techniques as a new technological approach to set up a non-invasive and non-destructive evaluation procedure for structural health monitoring of infrastructures.