Nondestructive Evaluation and Monitoring Technologies, Documentation, Diagnosis and Preservation of Cultural Heritage

As part of the innovative research entitled «Integrated Diagnostic Research Project and Strategic Planning for Materials, Interventions Conservation and Rehabilitation of the Holy Aedicule of the Church of the Holy Sepulchre in Jerusalem», conducted by National Technical University of Athens NTUA in agreement with the Jerusalem Patriarchate (The Joint Agreement and the Status Quo authorize the Greek Orthodox Patriarch of Jerusalem, in constant cooperation with the initiators of the three Christian Communities, the guardians of the Holy Sepulcher, the Patriarch of Jerusalem, Theophilus III, the Holy Land of the Order of the Franciscans, Pierbattista Pizzaballa (until May 2016), present Latino Patriarch in Jerusalem, Fransesco Patton (from June 2016) and the Armenian Patriarch in Jerusalem, K. Nourhan Manougian, to coordinate all the scientific, technical and management structures of the project.), occurs the following contribution on «Diagnostic research of the Dome of the superstructure of the Holy Edicule of the Holy Sepulchre in Jerusalem – Suggestions for maintenance and rehabilitation». The goals of the work are˙ the architectural documentation of the form of the Dome, the way it was constructed, the diagnosis of decay and pathology of its construction materials, the maintenance and rehabilitation proposals. First crucial step towards achieving the aforementioned was to conduct diagnostic investigation, through macroscopic observations, of the current situation of the Dome. The next step was to use non-destructive testing techniques (IRT, GPR, Endoscope, FOM) in order to obtain useful information regarding the construction way. Moreover, by using in situ measurements, the geometry of the structure was revealed, the sizing of the individual members was completed and thus it was possible to illustrate the structure in 2D and 3D designs. Finally, an illustrated model of the deformations of the structure was created and based on its results maintenance and recovery solutions were proposed.

In this work, an approach regarding the representation of a monument in combination with building material documentation information (deriving from non-destructive techniques) is presented. Through this approach, data incorporating architectural, surveying and building material documentation information are aggregated with the 3D documentation model, leading to valuable information regarding the preservation state of a monument. The illustration of the Pythian Apollo ancient temple, located in the Ancient Acropolis of Rhodes, Greece, aims to highlight the manner in which the fusion of multilayered information can contribute to the diagnostic study of a monument, ultimately leading to its sustainable protection through time. Information deriving from the three dimensional documentation of the monument is enriched with information deriving from non-destructive techniques (Ground Penetrating Radar, Infrared Thermography, Digital Microscopy) in combination with historical and architectural data and in-situ visual inspection observations. In addition, information regarding quantitative data can be acquired, facilitating future conservation interventions.

For decades, dating of Roman Terra Sigillata pottery was assessed by visual inspection. Since the ornaments and indentations on the ceramic surface are characteristic for the manufacturing workshop in the Roman Empire, archeologists have used chronological catalogues to assign the sherds to its time period. This paper should underpin the application of image-based nondestructive testing (NDT) methods as a powerful instrument for obtaining data, which allows to extract predominant features for later classification. At first, an overview ist given to a variety of non-invasive inspection technique with particular focus on digital photography and infrared (IR) thermography. To receive enhanced spectral information, IR thermography is proposed complementary to visible light photography in an experimental study. Furthermore, different image processing techniques are applied to reveal their potential for enhanced feature extraction. Finally, the paper should give rise for the identification of the manufacturing period and the constructor’s fingerprint of Terra Sigillata pottery at a later stage.

During the byzantine period gold-leaf glass tesserae were used in abundance for the creation of wall mosaics for the adornment of Byzantine churches. Metal-leaf glass tessera is a sandwich structure of two layers of glass (the support and the top glass) enclosing a metal leaf and its characterisation necessitates a more sophisticated approach compared to other glass tesserae. Studies of gold-leaf glass tesserae have been based on destructive analysis (cross-section analysis), however cultural heritage objects address for a different approach. The technical progress and accessibility to more elaborate techniques could facilitate a non-destructive research. The aim of this work is to present the potentials of a non-destructive and non-invasive methodology for the analysis of byzantine gold-leaf glass tesserae using ion beam techniques. The study of gold- leaf glass tesserae was carried out at the Byzantine Monastery of Daphni (11th century) Greece. The research combined systematic examination of tesserae and analysis of selected samples. Tesserae were analysed as received, using mainly Scanning Electron microscopy coupled with Energy Dispersive x-ray Spectroscopy (SEM/EDS) and Ion beam techniques. In the context of this contribution the results will be presented to demonstrate the efficiency of the selected methodology. μ-PIXE/PIGE analysis provided elemental analysis for both the glass layers and via elemental maps combined with photographic recording of analysed areas, direct information for technological features.

Infrared Thermography and evaluation (IRT) is a non-destructive testing technique, with a wide range of applications in the field of cultural heritage protection. In this study, IRT was used for the investigation of the temple of Hephaestus, one of the most well preserved ancient Greek temples and a great example of Architecture of Classical Times. There was an attempt to apply this IRT technique in a systematic way, in order to evaluate the most important factors affecting its performance. The examined factors examined fall into three categories: the first ones are climatic conditions (air temperature, relative humidity, solar radiation, wind speed); the second ones are factors related to the building itself (materials, geometry, microclimate) and thirdly factors associated with the capturing of the thermal image (shooting time, angle, distance). For those reasons, thermographic inspection of the monument was conducted in all four seasons of the year at different distances and different times throughout the day. IRT with the aid of suitable software has proven to be a valuable method for monitoring temperature changes of marble through time.

Plaka Bridge is a traditional one-arch stone bridge, built in 1866 above the waters of Aracthos river, in Epirus, Greece. The bridge was the largest one-arch stone bridge in Greece and the Balkans and one of the largest of its type in Europe. The bridge collapsed on 1 February 2015, following heavy rains in the area, the only remaining parts consisted of the western part including the western auxiliary arch, and the eastern entrance. Immediately after the disaster, the National Technical University of Athens formed a scientific expert committee which undertook in-situ assessment and provided a comprehensive report on the restoration of the Plaka Bridge. More recently, as part of the planned restoration project, ground penetration radar (GPR) was utilized to study the interior structure of the surviving western abutment of the bridge, in order to provide crucial information regarding the internal layering of the bridge, the presence of wooden elements that provided cohesion between load-bearing structural elements of the bridge and its support, as well as assess the state of preservation of the surviving parts, prior to the commencement of the bridge reconstruction. GPR revealed that potentially parts of a bridge constructed earlier than the current one are embedded within the western abutment. In addition, linear patterns corresponding to wooden elements were revealed that form a complex pattern within the surviving western part of the bridge. The information provided by GPR is crucial for the design and implementation of the appropriate restoration and rebuilding work, as it is planned that some of the original parts of the bridge will be retained in the reconstructed new bridge.

The Church of the Holy Sepulchre in Jerusalem is one of the most important religious sites of Christianity. It dates back to 326AD, when Emperor Constantine I ordered the construction of a basilica incorporating the Tomb of Christ within an Aedicule, and the hill of Golgotha. The Aedicule has undergone many reconstruction phases and restoration interventions, while sustaining many damages throughout its rich history. Recently, a project regarding conservation, reinforcement and repair interventions for the rehabilitation of the Holy Aedicule was successfully implemented. As part of this rehabilitation Works, ground penetrating radar (GPR) was employed for the survey of the Holy Aedicule to reveal the internal structural layers of the structure. Information from historical documentation and architectural analysis were correlated with findings from GPR prospection. This transdisciplinary approach allowed the elucidation of the structural evolution of the Aedicule. It revealed remnants of the original living rock of the 4th century Aedicule, surrounded by type of masonry dating to the Byzantine period, to the Crusader period and to 19th century major reconstructions. In addition, GPR and architectural analysis of the Aedicule’s structure revealed remnants of characteristic features of the 11th century Aedicule and large structural parts of the previous Aedicule below the height level of these two Domes.

In this work, we present the development of a database as a tool for cultural heritage information management. Additionally, the database must be suitable for the semantic analysis of the stored information permitting deriving conclusions and assessment of protection interventions. Concretely, the database should be capable of storing information regarding the conservation and restoration materials of the cultural heritage monuments, as well as the methods and techniques used each time. Technological developments in the field of non-destructive techniques have enhanced their usefulness in the field of built cultural heritage protection, and are indispensable tools for the characterisation of materials, detection of wear and degradation of materials, assessment of interventions’ effectiveness and evaluation of compatible materials and conservation interventions. For this reason, the database should be able to support, besides textual information, the storage and manipulation of multimedia information also. This means that the database will be able to store images of the optical spectrum, thermal and multispectral images describing the various aspects of application of restoration methods on specific cultural heritage sites or on specific materials in laboratory environment. Potentially, this database could support and store optical descriptors based on MPEG. Moreover, to ensure interoperability of the database with third-party decision support systems, we avoid the development of a conventional relational database. Instead, we developed the presented database using the JSON protocol. This protocol, except interoperability, provides the opportunity to perform complex database queries and respectively, get complex answers. Finally, it allows the organization of information in several abstract layers, which permits currying out appropriate ontologies that can describe the features of the stored data. Implementation of the developed interoperable semantic-based database is presented in a consolidation scenario considering conservation interventions in monuments and historic buildings in the island of Rhodes, Greece.

Non-destructive testing is used for many applications in the cultural heritage protection field. In this study three such sensing techniques, portable digital microscope, infrared thermography, georadar were used for the in site investigation of the ISIA building at the historic center of Florence. This work was a sub-action of a research program called MEDNETA; “MEDNETA- Mediterranean cultural network to promote creativity in the arts, crafts and design for communities’ regeneration in historical cities”.

Florence was selected as a case study city with ISIA building (Higher Institute for Artistic Industries), a university for education in the field of industrial design. This building is situated at the historic center and is a part of the Museo INNOCENTI complex. The building during the diagnostic campaign undergone redesign and renovation works, without although any changes in its use.

The in site diagnostic study was conducted by National Technical University of Athens (NTUA) research team in September 2014. Main aim of this investigation was the characterization of building materials and their decay diagnosis, based on guidelines prepared by NTUA research team. For this reason the above mentioned non destructive techniques were applied. Based on the EN Standard 16096-2012 the overall building preservation state could be classified in the overall preservation category characterized as “good”.

Thousands of people, agents, institutions and scientists from around the globe demonstrated their interest, fought against the mud and the time for not missing a single page of the Historical Archive of Communist Party of Greece (CPG) after a big flood. Fungi are growing in wet paper with accelerating pace. The building of the Central Committee was transformed in a large cleansing laboratory for removing the mud and drying the paper. The most challenging difficulty from the very first days was the volume of the material in need for rescue. In a short interval, the battle against time and fungi took place not to miss a single page. At the same time, the huge inexperience of dealing with catastrophes of such size was prevalent too. The steps were followed according to the bibliography [1‐4, 10, 25, 26]: Placing the ‘muddy’ material into low temperature fridges to cease the accelerating speedy development of the mould, gradual cleansing of the material from the mud and other litter, drying the material, decontamination-sterilization in special closets of 25 m³, space configuration with humidity and temperature conditions defined by the international literature and placement of the dried material, chemical treatment (De-acidification–Neutralization), solidification and restoration with the use of Japanese preservation papers, placement of the material into folders and boxes with antacid – antifungal protection and special environment conditions, computerization and electronic storage (digitalization). The preservation and restoration laboratory that was created is not only providing precautionary and substantial preservation of the archival material but also checking the process of the implemented methods. The slowing-down of its chemical downgrade is the primary target [16, 20, 21]. Securing stable humidity and temperature conditions defined by the international literature was the first big step for the future physicochemical course of the material [1, 4, 6, 13, 27].

The above conditions are contributing at different levels to the non decomposition of cellulose.

The checking of the processes in accordance with the time is required, because the longevity of the archival material is a direct function of the stability of the preservation conditions and of the successful physicochemical methods that are implemented. For the first time there is control of the processed and non - archival material with Scanning Electron Microscopy (SEM) – micro-analysis Energy Dispersive Spectrometer, (EDS) and through X-Ray Diffraction (XRD). We believe that this will contribute to the further deepening of the factors conducing to the decomposition of the cellulose chain, as well as to the better searching of the various chemical actions’ mechanism that lead archives, libraries and museums to destruction. At the same time, the digitalization of the archive and the minimal – only absolutely necessary - use of the original material provide today the best conditions for its future physicochemical course.

In this paper, the response of a restored part of the ancient Temple of Pythian Apollo under strong seismic motions is examined. The monument is located on the ancient Acropolis of Rhodes and, in its present condition, consists of a single free-standing column and a colonnade composed of three columns and an entablature. Only a few drums contain ancient parts found in the excavations, while the rest is newer material, placed during the Italian restoration of 1937-38. The examined structure corresponds to the monument after a probable restoration scenario, which accounts for the replacement of all complements that were installed during the Italian restoration with new parts from natural or artificial stone. The performed investigation concerns the response of the structure under six strong seismic excitations, chosen to be compatible with the tectonic environment and past seismic events, scaled to two levels of ground acceleration, corresponding to return periods of 500 years and 1000 years. The structural analyses were performed with the finite element software ABAQUS. The monument was modelled using three-dimensional deformable finite elements, while special attention was paid to the modelling of the mortar that connects structural members, as well as the interface between the drums, where rocking and sliding are allowed. The results of the analyses lead to various conclusions about the response of the structure under the considered seismic scenarios, including the danger of collapse of the monument, the residual displacements induced by the earthquakes, the stress levels that develop in the structure and across the interfaces and the expected damage to the structural members. Based on these results, conclusions are drawn regarding the adequacy or not of the strength capacity of the proposed new parts (natural and artificial stones and connecting mortar), while the possibility of damage to ancient parts during earthquakes is also examined. The main conclusion is that, if the structure remained undamaged, it could survive five out of six of the examined earthquakes, except of the stand-alone column which collapses in half of them. However, this is not the expected situation, since damage will occur to several new and ancient parts during a strong seismic event, increasing significantly the vulnerability of the structure and the risk of partial or total collapse.

The artificial oxalate method has been thoroughly studied over the last decades as a compatible and performing protective treatment for marbles and other calcite stones. In this study, the most widely used synthesis (5% w/v ammonium oxalate aqueous solution) was applied by brushing on pentelic marble surfaces and assessed in terms of surface texture alterations. Three differently textured marble surfaces were produced in terms of roughness levels, and were measured by a mechanical roughness meter. Scanning Electron Microscopy (SEM) proved to be an indispensable tool in order to investigate the morphological alterations of the process through the comparison of the original surface texture with the one induced by the conversion of calcite into calcium oxalate. The calcium oxalate formation was verified by Raman spectroscopy, where whewellite was clearly detected. Finally, the digital imaging processing of the SEM images served as an indicative tool for the quantification of the process, regarding the surface percentage that is covered by the newly formed calcium oxalate.

Ground penetration radar was used at the historic building of the “Colegio del Arte Mayor de la Seda de Valencia”, to assess the structural state of the building, by focusing on identifying and locating major internal cracks or interfaces that could pose structural problems to the building, and on providing general information about the construction technology of the masonry. Through the analysis of the various scans at characteristic areas of the historic building, GPR identified and allowed correlation of crack clusters and revealed hidden features, such as potential hidden arches, within the masonry that were not observed macroscopically. It was revealed that the deformation thrust of the eastern façade of the building was responsible for a cluster of cracks along its longitudinal axis at the interior of the building. A similar behaviour was correlated with a major crack behind the main maiolica tile mosaic, along the transverse axis of the building.

Masonry structures are complex systems that require detailed knowledge and information in order to determine their behavior under seismic stimulation. Therefore, an appropriate modeling is a necessity for their reliable design. Moreover, the use of consolidates is a common general preservation action, but no extensive research has been made on historic masonries. In the present paper, an innovative approach was applied in the historic building «Medikon Mansion» in Mani, for the realistic depiction of its behavior under seismic loading. This was done by creating a Finite Element Model which is behavior after the application of three different consolidation proposals of inorganic (HAP) and alkoxysilanes (ES and TEOS) materials was investigated. The FEM was created with the aim to assess appropriate retrofit innovations and materials according to criteria of compatibility and performance. This is an inclusive methodology to approach historic buildings and thus laboratory tests were performed on samples from the local quarry, before the creation of the FEM, in order to create a dynamic analysis of the building in contrast with the most static researches. The analysis showed that the TEOS alkoxysilane proved to be the most effective consolidate. Moreover, the probability of failure due to tensile strength was reduced, but not to a satisfactory degree, in contradiction to the notable reduction that was noticed to the fundamental period (up to 8%) and displacements (up to 30%) of the mansion.

During the last decade, documentation and three dimensional (3d) reconstruction of archaeological sites and buildings have proven to be a valuable tool in terms of preservation and restoration processes. Moreover, 3d virtual models are used for the representation of cultural heritage assets, in a specific state of preservation at the time of a chosen period. In addition, diagnostic study of monuments with nondestructive testing methods is growing as common practice, for the assessment of their preservation state. A research study of the Acropolis of Erimokastro, an archaeological site in Rhodes Island, Greece, is presented, that concentrates on the use of various documentation methods and their integration for the assessment of the site’s preservation state. Initially, thorough historical documentation was performed. Geometric documentation was conducted using a drone and close range terrestrial photogrammetric processes. Infrared Thermography was applied in selected areas and more specifically in the exterior walls of the Acropolis, for the assessment the preservation state of the walls, for the detection of thermal conductivity of the building materials and decay patterns of the site. The goal of the study is to evaluate the preservation state of the Acropolis, through the integration of various multidisciplinary data including geometric, historical and building material information. Overall, the paper presents the employed 3d surveying techniques, the obtained 3d results and concludes in the documentation processes for analyzing ancient walls within a particular environment and the integration of infrared thermography on the remaining walls of the archaeological site for its sustainable rehabilitation in the future.