Issue 46

A. Maione et alii, Frattura ed Integrità Strutturale, 46 (2018) 240-251; DOI: 10.3221/IGF-ESIS.46.22 242 heating; this approach provides mainly qualitative data about the object. The active approach, instead, requires artificial heating usually obtained with the light emitted by flashed lamps, lasers or other light sources. Maierhofer and Roellig [24] presented several case studies showing the effectiveness of the impulse-thermography for the investigation of cracks, delaminations and masonry structure behind plaster. Both active and passive approaches were recently adopted by Cantini et al. [25] in the study of the vault of the Assembly Room within the Palace of the Academy of Sciences in Torino; the active approach allowed detecting the presence of detached areas of the stuccowork, while the passive approach was used for the identification of the structural elements of the wooden frame of the vault. The passive approach has been used for the investigation of some vaulted structures in the Capodimonte Museum, as described in this paper, and the qualitative information obtained on their constructive typology have been interpreted and coordinated with other sources of information; such integrated approach has allowed achieving a proper characterization of the constructive features of the horizontal structures upon the first level of the Museum. Hence, in the following sections, the case study is firstly presented highlighting the critical issues raised from a first step of visual inspection; then the findings of the thermographic survey are presented together with short references to the basic principles of this technique. Finally the instrumental findings have been interpreted and integrated with other sources of information providing a classification of the analysed horizontal structures that has been useful for the definition of a proper model of the building to evaluate its seismic safety. Only the results of the visual inspections and thermographic survey together with the discussion on the critical issues are presented in this paper, while more details on historical analysis, geometrical/architectural survey and damage inspections can be found in [4]. T HE CASE STUDY OF THE C APODIMONTE M USEUM IN N APLES : CRITICAL ISSUES he case study analyzed in this paper may assume a paradigmatic relevance in drawing up an integrated approach to the identification of the structural features of ancient masonry buildings. In particular, the attention is focused on the horizontal structures covering the rooms on the first level of the Capodimonte Museum. These rooms were originally meant to royal apartment, but in the '50s of the last century they were transformed according to the project of the architect De Felice to host the exposition of the painting collection of the Museum [7]. The available documentation of the project, however, shows that it was aimed at preserving the historical asset of the rooms by adopting architectonical solutions that try to simulate the aspect of the ancient structures, as will be confirmed by the instrumental investigations described in the following section. According to the Italian Guidelines [1], a basic level of knowledge was firstly achieved through the visual inspections and the architectural survey; these activities together with the verification of the data derived from the documentary and bibliographic sources allowed identifying the essential geometrical and constructive features of the building, as described in detail in [4]. However, at the end of this first phase of knowledge some problematic aspects arose, requiring deeper investigations. They mainly concern the characterization of the constructive typology of three couples of adjacent rooms, characterized by a similar configuration and indicated with the numbers 9 and 49, 10 and 48, 11 and 47 in the plan layout of the first floor (Fig. 2a). The vaults of these rooms are a type rather common in Italy known as a schifo or mirror vault, and two of them are painted vaults (no. 9 and 10 in Fig. 2b and 2c, respectively); all of them, however, are supported by structural masonry walls on three sides, while on the fourth side there is only a thin wall of about 20 cm which divides the adjacent rooms. This configuration can also be found in other rooms, such as 17, 18, 33 and 53 in Fig. 2a, while the mirror vaults covering most of the rooms on the first level are conventionally supported, even if not in all cases with load- bearing function. The two large and double height rooms at the north-eastern and south-eastern corners are covered by cloister vaults overlaid by r.c. structures, while other mixed and overlapped typologies are present on the other rooms, as investigated and described later in the text. Hence, in order to understand whether the vaults of adjacent rooms have decorative or structural function, the following hypotheses were formulated on the basis of the critical analysis of the historical documentation and of the geometrical survey [4]. According to a first hypothesis, the two adjacent rooms derive from the partition of a unique space covered by a structural masonry vault, maybe required by the exhibition needs of the Museum. With this transformation, three sides of the original vault were preserved, while a wooden structure was built on the fourth one, resembling the profile of the vault. This hypothesis is supported by the inclination of the fourth side of the vault that appears considerably more pronounced. Another possible hypothesis is that the present visible vaults are not load-bearing, but they have a timber structure that repeats the shape of the original masonry vault. This kind of solution, on the other hand, was found out in the rooms 51 and 52 (see Fig. 3) which also result from the division of a unique space; in fact, by approaching the narrow space behind T