Damage detection on reinforced concrete framed structures using a band-variable filter

Structural Health Monitoring (SHM) aims to increase the knowledge about linear and non linear dynamic behaviour of structures in order to develop accurate strategies of analysis for the safety assessment. Particularly, structural monitoring, especially for structures located in seismic prone areas, assumed great importance for the possibility to provide useful information about the state of the health of strategic structures and infrastructures over time and to perform an objective quick estimate of the damage occurred on structures just after a seismic event. It is known that the occurrence of structural damage, for any kind of structure, it is able to changes its dynamic characteristics over time. Generally, the main parameters conditioned by this problem are periods of vibration, equivalent viscous damping factors and mode shapes. Several authors showed that also the variations of the modal curvature are strictly related to the damage occurred on a structure. Moreover, using the mode curvature as a control parameter it is also possible to localize where the damage occurred along the height of the structure. In order to analyze the nonlinear behaviour of a general structure, and localize a possible damage, a band-variable filter based on the Stockwell Transform has been proposed. Basing on the results of nonlinear numerical analyses and shaking table tests on a scaled model, this paper shows some example of application of the proposed methodology to identify and localize damage occurred on framed reinforced concrete structures after an earthquake.