Extended Tromograph Surveys for a Full Experimental Characterisation of the San Giorgio Cathedral in Ragusa (Italy)

Abstract

Geophysical surveys are widely used to reconstruct subsoil seismo-stratigraphic structures with a non-invasive approach. In this study the geophysical surveys were carried out with the aim to characterise the San Giorgio Cathedral in Ragusa (Italy) and the area on which it is built from a dynamic point of view. A 3D subsoil model was realised through the integration of two active (i.e., seismic tomography and multichannel analysis of surface waves) and one passive seismic technique (horizontal to vertical spatial ratio). The instrumentation used for the latter method consists of a tromograph (Tromino®), which is also employed for the characterisation of the building, focusing on the façade and the dome, by means of an ambient vibration test, processed through the standard spectral ratio and frequency domain decomposition methods. Integration of the 3D model, showing the distribution of areas with different physicomechanical characteristics, enables identifying anomalies that are likely attributable to the remains of the ancient Byzantine church of San Nicola. Four lower modes mainly involving the two investigated macroelements are identified. The experimental results outline the advantages of the use of the tromograph both for soil and structural characterisation, especially for massive masonry buildings located in areas with high seismic hazard.

Implementation of a Condition Monitoring Strategy for the Monastery of Salzedas, Portugal: Challenges and Optimisation

“…This produces signals with low amplitude and high levels of noise, which affect the identification of higher modes, commonly local and more sensitive to damage, limiting the investigated bandwidth to a few hertz [45,47,48]. Moreover, the dynamic response of the built CH is commonly governed by its components and macro-elements, which are complex to identify through ambient vibration and could be evident only at specific measurement points [49,50]. Finally, it is worth noting that the intrusiveness of the sensing systems to the view and their obstructiveness for operation should be minimised, especially for long-term monitoring, as with any other measures affecting CH fruition, aesthetics, and heritage value [47,51,52].…”

Microtremor Recording Surveys to Study the Effects of Seasonally Frozen Soil on Site Response

“…Consequently, this approach can lead to inaccuracies in determining the predominant frequency of the microtremor spectrum, making it challenging to estimate the site amplification factor [ 11 ]. On the other hand, numerous studies have demonstrated that the microtremor horizontal-to-vertical spectral ratio method (HVSR) effectively eliminates the influence of the vibration source on the site dynamics analysis, resulting in predominant frequencies that are more representative of the actual site frequencies [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ]. As a consequence, many recent studies have employed the microtremor HVSR method to determine the site characteristic parameters.…”