Integrated and multi-scale NDT for the study of the Architectural Heritage Luigia Nuzzo* a , Nicola Masini b , Enzo Rizzo c , Rosa Lasaponara c a Research Institute for the Environment, Physical Sciences & Applied Mathematics (EPSAM), Keele University, Staffordshire, ST5 5BG, U.K.; b Istituto Beni Archeologici e Monumentali, IBAM-CNR, C.da S.Loja – 85050 Tito Scalo (PZ), Italy; c Istituto di Metodologie per l’Analisi Ambientale, IMAA-CNR, C.da S.Loja – 85050 Tito Scalo (PZ), Italy ABSTRACT The restoration of artistic and architectural heritage represents a bench mark of the cultural development of a society. To this end it is necessary to develop a suitable methodology for the analysis of the material and building components which are usually brittle and in a poor state of conservation. The paper outlines the advantages and the drawbacks in the use of Non-Destructive Testing (NDT) techniques and the need to integrate them in order to obtain a reliable reconstruction of the internal characteristics of the building elements as well as the detection of defects. In the study case we used Ground Penetrating Radar (GPR), infrared thermography (IRT), sonic and ultrasonic tests to analyze a 13th century precious rose window in Southern Italy, affected by widespread decay and instability problems. The theoretical capabilities and limitations of NDT are strictly related to the frequency content of the signals used by the different techniques. Therefore, integrating several physical methods and using different frequency bands allowed as a comprehensive, multi-scale approach to the restoration problem. This revealed to be a proper strategy in order to get high-resolution information on the building characteristics and the state of decay which could support a careful structural restoration. Keywords: Non-Destructive Testing, ground penetrating radar, infrared termography, sonic and ultrasonic tests, rose window, architectural heritage 1. INTRODUCTION Non-destructive testing (NDT) techniques are becoming increasingly popular in the study and restoration of the Architectural Heritage. Any repairing work of an architectural building needs a detailed knowledge of its state of preservation and of the original construction techniques. While in the past the only way for obtaining such kind of information was based on destructive tests (coring), nowadays an increased awareness of the cultural value and brittleness of the artifacts to be restored favors the use of NDT, such as Ground Penetrating Radar (GPR), infrared thermography (IRT), sonic and ultrasonic tests. Previous studies (Inagaki et al., 1999; Maierhofer and Leipold, 2001; Binda et al., 2003; Avdewlidis and Moropolou, 2004) have shown the potential of each of the above techniques to cast light on some important aspects of cultural heritage preservation. In most cases only one or two techniques have been employed, whereas the complexity of the present case history and the multiplicity of issues to be addressed required an integrated and multi-scale approach (Nuzzo et al., 2005; Capriuoli et al., 2006; Liberatore et al., 2006; Masini et al., 2007) to complement the laboratory analyses for the material characterization. The Cathedral of Troia (Apulia, Italy) was built between 1093 and 1120 A.D. and is the masterpiece of the Apulian Romanesque architecture (Belli D’Elia, 1998). Its façade (Fig. 1a) is 18.28 m wide and 19.90 m high. The basement is decorated with seven blind arches, rhombs and oeil-de-boeufs characterized by chiaroscuro effects through the use of the whitish calcarenite stone of Castelluccio and the greenish sandstone of Roseto. The central tympanum consists of two round arches, the outer arch resting on two couples of columns in reused marble, the inner arch richly sculptured with plastic elements and bas-relief. Inside this arch there is the rose-window (Fig. 1b). It has a 6 m diameter and consists of 11 twin columns, outer and inner, in stone and reused marble, connected to a central oculus and to a ring of trapezoidal elements decorated with arched ribworks. Between the twin columns there are 11 triangular carved panels with different and strongly symbolic geometrical patterns. According to visual inspection, mineralogical and petrographic studies, different materials have been used for the different architectural elements: fine grained limestone for the central oculus, Remote Sensing for Environmental Monitoring, GIS Applications, and Geology VIII, edited by Ulrich Michel, Daniel L. Civco, Manfred Ehlers, Hermann J. Kaufmann, Proc. of SPIE Vol. 7110, 711015 · © 2008 SPIE · CCC code: 0277-786X/08/$18 · doi: 10.1117/12.801313 Proc. of SPIE Vol. 7110 711015-1 2008 SPIE Digital Library -- Subscriber Archive Copy