What is Ambient Vibration Measurement

Historical churches have shown a dramatic vulnerability in several recent earthquakes, especially when they are adjacent to bell towers. Due to their great number and their societal relevance, low cost and nondestructive survey and investigation procedures are necessary for the seismic assessment. Accurate and fast geometric models can be obtained through digital photo-modeling, and they are the base for finite element models. These models can be updated through ambient vibration testing, which delivers a robust estimate of the fundamental period of the building especially in the case of cantilever-like bell towers. Elastic modulus and boundary conditions can be evaluated through numerical and physical comparison, provided that in situ sampling suggests a masonry density value. Then, compressive strength can be estimated, yielding a more robust seismic assessment. The proposed procedure is applied to the Cathedral of Matera, Southern Italy.