DIAGNOSTIC INVESTIGATION OF THE STONE PILLARS OF S. NICOLO’ L’ARENA, CATANIA

Saisi ¹, L. Binda ¹, L. Zanzi ²

1. Dipartimento di Ingegneria Strutturale, Politecnico di Milano, Piazzale L. da Vinci 32, 20133 Milano, binda@stru.polimi.it, saisi@stru.polimi.it.
2. Dipartimento di Elettronica ed Informazione, Politecnico di Milano, Piazzale L. da Vinci 32,20133 Milano, zanzi@elet.polimi.it

ABSTRACT

The church of S. Nicolò L’Arena in Catania built in the 17th century has been subjected to various important damages due to earthquakes and the Etna volcano eruption. It has a large dome and vaults supported by very massive stone pillars. The church was partially rebuilt after the above mentioned damages. The original pillars, which remained at the entrance and at the first arcade, were built with a different construction technique than the reconstructed pillars. All are made with volcanic stones and lime mortar. Nevertheless the original pillar have a highly inhomogeneous section with a mixture of large irregularly cut stones and rubble material. The other pillars have a multiple leaf section with large regularly cut stones and rubble filling.

After an earthquake, which struck the Eastern part of Sicily in 1990, the structural elements of the church as the dome and the vaults were damaged and the appearance of vertical cracks on the original pillars were detected. It is not clear whether those cracks were already visible and were simply propagating during the earthquake.

An investigation programme (including sonic, radar, flat jack, coring, boroscopy, etc.) has been recently planned to design the preservation and restoration actions.

Very interesting information were expected by stratigraphy of the section by coring, flat jack tests and sonic tomography; also radar tests were applied. Sonic tomography is a powerful method to obtain information on the conditions of a structural element. In general, the velocity distribution is an indication of the elastic properties of the element.

The results obtained from sonic tests were compared to the results of the other type of tests in order to set up an investigation procedure useful for these cases. The paper presents and discusses the preliminary results of the research carried out by the authors.

Key words: diagnosis, non destructive testing, sonic test, tomography, flat jack

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