Issue 60

F. Greco et alii, Frattura ed Integrità Strutturale, 60 (2022) 464-487; DOI: 10.3221/IGF-ESIS.60.32

Geometric survey The geometry survey of an ancient and complex building is a challenging task because of various issues, such as the presence of articulated shape geometries, the differences in the size of structural elements, and the difficulties of correctly identifying all the portions of the building. The survey of the Cathedral has been performed through a 3D laser scanner procedure, which involves the construction of a dense 3D points cloud of the building (see for instance [36]). Because of the massive size of the Cathedral, different locations of the laser scanner have been considered, thus recording many clouds of points. The achieved clouds have been subsequently converted to triangular meshes, forming the surfaces of the sampled parts (Fig. 1(B)). Figs. 2 and 3 show the output of the triangular mesh operations obtained via laser scanner procedure, useful to achieve a preliminary representation of the geometric schemes of the whole structure. Finally, triangular meshes have been transformed into geometric entities, thus providing the final geometrical representation of the Cathedral. Besides, a thermographic analysis has been performed to recognize discontinuities in the masonry walls and to check the presence of reinforced concrete (RC) elements embedded in masonry structures. The actual configuration of the Cathedral is different from the original structures, that exhibited a Latin cross plan. These differences are present due to the several events that changed the structural system over the decades, such as the earthquake of the 1783 and the damage caused by the Worl War II bombing.

Figure 2: Vertical section derived from the 3D laser scanner survey.

Figure 3: North-west (A) and South-west (B) general view derived from the 3D laser scanner survey.

The central nave is 30.70 m long and 10.95 m large, whereas the transept is rectangular with a length of about 14.00 m and a width of 13.00 m. Both the central nave and the transept have a height of 19.60 m and are covered by a gable roof made of reinforced concrete truss structures. The intersection of the central nave with the transept defines the core of the

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