Vibration-Based Test Results for the Investigation of the Infill Masonry Wall Damage

Infills are one of the most common non-structural elements worldwide adopted to build external and internal partition walls in framed structures. Many types of infills can be encountered in practical applications, characterized by different construction typologies and materials, but the most adopted ones are those realized with masonry. It is well known that infill masonry walls suffered lot of damage in the past as a consequence of earthquake excitations and, moreover, they were cause of undesirable effects on the structural seismic performance, such as the activation of soft story mechanisms and shear failure of short columns. For these reasons, the infill contribution on the seismic behaviour of buildings should be investigated both during the design process of new structures and the assessment of the existing ones. The aim of this paper is to investigate the usefulness of vibration data for the damage detection in infilled frame structures starting from the tracking of both the stiffness and modal properties. To this aim, an experimental campaign was performed on a laboratory steel-concrete composite frame with infill masonry walls. The tested mock-up was subjected to stepped-increasing cyclic displacements that produced a progressive in-plane damage of infills, up to their complete damage. In the meantime, vibration-based tests characterized by different level of input excitation provided to the structure, were performed to capture the effects of the infill damage on the mock-up global dynamic response. Results provide useful information for the detection and tracking of damage to non-structural elements during and after low and moderate seismic events, contributing to a better interpretation of data provided by structural health monitoring systems. Finally, a monitoring strategy suitable for new infilled buildings is proposed, with the main aim of providing a contribution in the context of differentiating between structural and non-structural damage, especially in case of blind monitoring.