Chiara Iacovino

Damage Assessment on Framed Structures Through Regression Models Retrieved by Nonlinear Numerical Analyses

Nowadays, Structural Health Monitoring is certainly a topic of great interest both in the research and in the professional field as evidenced by the large number of applications and systems installed all over the world. A permanent monitoring system could be installed in order to identify a possible damage occurred on framed structures after moderate/destructive earthquake. Furthermore, it could be an useful tool for evaluating the service condition and the remaining service life of a structure. Most of simplified methods for structural damage detection are based on the evaluation of the dynamic characteristics evolution associated to the fundamental mode of vibration of a monitored structure. Particularly, the variation of parameters such as eigenfrequencies, equivalent viscous damping factors and modal and/or operational mode shapes has been evaluated and analyzed in order to identify structural damage. Methods based on frequency variation can be applied to detect damage, but they are not able to localize structural damage. Instead, to this aims, methods based on the evolution of modal shapes and/or of their derivatives such as mode curvatures could be more effective. Aim of this work is the improvement of an existing method for damage localization on framed structures based on the evaluation of the mode curvature change associated to the fundamental mode of vibration during an earthquake. The approach is based on the use of a nonlinear filter, the band-variable filter, able to extract the nonlinear response of each mode of vibration. The paper focuses also on the possibility to quantify the damage occurred on the monitored structure by considering the correlation among maximum value of mode curvature variation and the maximum inter-story drift. The regression model between these two parameters has been defined through nonlinear numerical models for different reinforced concrete framed structures designed for gravity loads only, with and without the presence of infill panels.

Experimental damage localization in a full-scale 7 story benchmark building under seismic excitation

In this paper two methods of damage localization previously proposed by the authors are combined to smooth the possible drawbacks and boost the advantages each of them. The Modal Interpolation Method (IM), recently proposed, is based on a damage feature defined in terms of the loss of smoothness (that is local increases of curvature) of the modal shapes induced by a local reduction of stiffness. Herein the combination of the IM with the Curvature Evolution Methods (CEM) is proposed. The CEM is based on the use of a Band-Variable Filter able to extract from recorded responses the nonlinear response of one mode of vibration enabling the detection of possible changes of a properly defined damage feature, during a single earthquake. In the CEM the modal curvature is assumed as damage feature. The combination of the two methods CEM and IM is carried out using the Band-Variable Filter to extract the nonlinear response of the structure and assuming as a damage feature the variation of the interpolation error computed at different times during the strong motion. The validation of the combined approach, named Interpolation Evolution Method (IEM), is carried out on a full scale experimental benchmark tested on the UCSD-NEES shake table.

ANALYSES OF THE SEISMIC ACTIONS RECORDED DURING THE 2016 CENTRAL ITALY SEISMIC SEQUENCE: OBSERVED VS CODE PROVISION VALUES

On August 24, 2016 at 03.36 a.m. (Italian time), a Mw 6.0 earthquake struck an extensive portion of the Central Italy. The epicentre was located among the municipalities of Accumoli (province of Rieti), Amatrice (province of Rieti) and Arquata del Tronto (province of Ascoli Piceno). After this first seismic event, from the academic point of view, several technical and scientific activities started with the aim to carry out preliminary evaluations on the characteristics of the seismic sequence, in order to interpret the possible effects of soil amplification in the areas affected by the earthquake and the damages observed on structures. The activities are continuing after the Mw 5.9 earthquake on October 26, 2016 and the Mw 6.5 earthquake on October 30, 2016. The strong motion recorded signals have been analysed in terms of peaks (PGA, PGV and PGD) and integral seismic parameters starting from data recorded by the closest stations to the epicentres. Several comparisons between the elastic response spectra retrieved from accelerometric recordings and the elastic demand spectra provided by the Italian seismic code (NTC 2008) have also been performed. 3923 Available online at www.eccomasproceedia.org Eccomas Proceedia COMPDYN (2017) 3923-3936