The usefulness of OMA for evaluating the health status of structures

The health monitoring and the safety assessment of buildings and infrastructures during their life cycle are of paramount importance for assuring the building use with acceptable risks for users, especially after the occurrence of earthquakes or other exceptional events, such as hurricanes, blasts or vehicle impacts. For strategic structures with public functions (e.g., bridges, hospitals, police and fire stations, schools, etc.) the structural health monitoring can provide useful information about the building status, in terms of damage on structural and non-structural elements; if the monitoring system reports alert situations through suitably installed specific sensors, visual inspections and destructive or nondestructive experimental tests can be also executed with the aim of supporting the decision-making process about the building use. The paper discusses about the effectiveness and usefulness of OMA in the assessment of the health conditions of buildings, and in its suitability within a structural health monitoring framework. An experimental campaign was performed on a laboratory steel-concrete composite frame with infill masonry walls: a progressive damage was produced to the non-structural components through cyclic load tests with increasing amplitude displacements, and vibration-based tests were performed with the aim of tracing the evolution of the frame dynamics and modal properties. Results demonstrate that OMAs are suitable for detecting the damage occurring to the non-structural components, while they are less useful in capturing the dissipative capabilities of the resisting nonlinear mechanisms that develop due to damage.