The practice of operational modal analysis (OMA) on civil structures and infrastructures has grown significantly in recent decades. Several methods have been developed and widely used on large concrete infrastructures such as buildings, bridges, dams and historic monuments. However, very few studies have been carried out on raw earth housing, despite the fact that a third of the world's housing is made up of raw earth buildings. Recent earthquakes in Morocco, Turkey and Nepal have demonstrated the importance of understanding the dynamic behaviour of these structures in order to assess their seismic vulnerability.

This study explores the use of operational modal analysis to assess the dynamic characteristics of rammed earth buildings. The objects of study are rammed earth buildings in the Rhône-Alpes region of France. Frequency domain decomposition (FDD) and stochastic subspace identification (SSI) methods are then used to determine the structure's eigenmodes. The modal frequencies identified are used to establish an initial estimate of the frequency ranges for rammed earth structures and to identify the physical parameters of rammed earth in real building. Besides, the initial damping of these structures is estimated, providing essential information for a better assessment of their seismic performance. The aim is to provide an initial overview of the vibratory behaviour of rammed earth buildings.

The development of the use of operational modal analysis will help to overcome the lack of standards for the earthquake-resistant design of raw earth structures.