Stone Ashlars Research Articles

Collaborative Workflow in an HBIM Project for the Restoration and Conservation of Cultural Heritage

ABSTRACT A restoration and conservation project for a building with heritage values requires an increasingly efficient and sustainable methodology. Based on a collaborative ‘Teamwork’ HBIM (Historic Building Information Modelling) project, this paper aims to describe the technical processes applied to a 16th-century historic building to support an open and interoperable workflow between the participating agents. The process is transparent and controllable by operators and disciplines, ensuring direct and continuous access to project data. The study focuses on implementing effective procedures for the identification and classification of heritage architecture. The first stage comprises the analysis of the geometry and materiality of the existing architecture, using data acquisition technologies such as Terrestrial Laser Scanning (TLS) and Structure-from-Motion (SfM) photogrammetry. The information modelling of the historic building begins with a medium level of knowledge, based on the metric survey and enriched by the materiality of the textures deriving from the point cloud. This enables a modelling approach that fits building components to the real geometry of the historic building, considering the deformations and irregularities that occur over time. In the next phase, the BIM project is developed through the analysis of the construction characteristics, materials, and architectural structuring in the historical evolution of the building. The difference between intervening in architectural heritage and new construction lies in the search for the transposition of construction techniques in walls with a long history, thus requiring classification and sectorisation of the various systems used. It is then required to segment the construction systems based on a semantic study of the walls that make up the envelope of the historic architecture. Programming objects in Python within the BIM platform enables the automated identification processes. The method is applied in the identification of the integrating elements of a larger construction entity, such as the stone ashlars of the masonry wall, and the classification by their construction-temporal dating. The main novelty of this research is the use of the object-oriented programming language (OOP), which automates operations based on an open-source structure and allows the operability of cataloguing, classification, and reuse characteristics.

Stone blocks surpluses? Reconstruction of the building process and architectural form of Marina el-Alamein hypogea

The monumental rock-cut tombs of the Graeco-Roman necropolis at the site of Marina el-Alamein on the Egyptian Mediterranean coast, today a sightseeing icon following restoration work by the Polish team, have produced significant information about the town, its inhabitants, and burial traditions. Different aspects of the tombs and their content have already been discussed, but without going into the details of the architectural building process. This paper focuses on ancient quarrying and masonry techniques in an effort to reconstruct the process as applied to the large hypogea. An estimate of the volume of stone material sourced during the execution of the underground parts of these tombs was compared with the reconstructed demand for stone ashlars used in the aboveground superstructures. The issue to be examined in this context is whether the tomb hypogea could have produced a surplus of stone building material, thus serving as a quarry for the city itself.

History, Geometry and Stereotomy in the Vaults of the Halle au Blé

This paper analyses the history, cultural background, geometric configuration and stereotomic apparatus of one of the most interesting buildings in the urban landscape of Paris between the eighteenth and nineteenth centuries, the Halle au Ble in Rue de Viarmes, also known in English as Corn Exchange. This building, which over the years underwent several formal, functional and structural transformations, is particularly interesting to scholars because of the innovations researched and designed by the French architect Nicolas Le Camus de Mezieres, who tried to solve some novel geometric and constructive issues drawing from available treatises, probably most of all that of Frezier. His contribution to the Halle au Ble includes the invention of particular vaulted surfaces assembled by blending stone ashlars and bricks.

THE MEMORY OF PLACES: THE SURVEY, REINVENTION AND RECONSTRUCTION OF A SMALL AGRICULTURAL ARTEFACT IN THE MOUNTAIN VILLAGE OF QUOTA, CASENTINO, ITALY

Abstract. The "history" of places exists as a stratification process of events that have occurred over time in a specific place, leaving more or less appreciable physical traces. The "memory" of the places, instead, is the result of a conscious choice of events to be handed down to future generations constructing the identity of a community and a recognisable image of places. It is in this sense that the project conducted in Quota, a mountain village in central Tuscany, Italy should be interpreted and set. The urban redevelopment process led to the design and reconstruction of a small agricultural artefact, particularly important to the local community given its location near a public fountain. Initially identified as the subject of an exercise to be conducted as part of the Thematic Seminar "Survey, redevelopment and redesign of architecture and environment", the redesign offered an opportunity to "re-invent" a neglected corner of the village taking as reference the traces of the ancient village fountains to create the plot of a new "story" involving the small local community. The reconstruction was carried out using traditional techniques with stone ashlars and cement mortar. To complete it, a corten steel staircase designed with reverse engineering methods and modelled using experimental 3D photo-modelling was created. The "Quota chestnut dryer" proved to be a virtuous process involving various subjects to enable the recovery of a degraded area, a possible model for the preservation of villages in the Apennines of central Italy, authentic sites of collective memory.

Determination of weathered degree and mechanical properties of stone relics with ultrasonic CT: A case study of an ancient stone bridge in China

A lot of cultural heritages in the world made up of or supported by stones are damaged seriously because of long-term weathering. It is necessary to assess the weathered degrees and stabilities of these heritages. In this paper, a procedure to assess the weathered degrees and stabilities of stone relics was put forward on the base of ultrasonic CT techniques. The procedure was applied to an ancient stone bridge in eastern China, Guyue Bridge constructed about 820 years ago. Firstly, P-wave velocity distribution profiles of stone ashlars of the bridge were obtained with ultrasonic CT techniques. Secondly, according to velocity ratio of the in situ P-wave velocities of the stone ashlars to the P-wave velocity of the fresh rock specimens of the same lithology with those of the stone ashlars, the weathered degrees of the stone ashlars were determined. Finally, the same rock specimens with different weathered degree, which were collected from a quarry near the historic bridge, were tested to get their P-wave velocities, UCS and elastic moduli, and the relations between the P-wave velocity and these mechanical properties were put forward. On the base of these relations, the mechanical property distributions of the detected stones could be obtained. In this study, two vertical sections of an ashlar in the historic stone bridge were detected by the assessment procedure. According to the assessment results, the two cross sections have different weathered degrees because of different stress states: higher weathered degree and lower compressive strength present to the section near the joint connecting two stone ashlars, where pressive stress is much stronger than that of the section far away from the joint. Correspondingly, the higher weathered section had worse physical and mechanical properties, which would be the key location for the stability of the old bridge.

Rampant Arch and Its Optimum Geometrical Generation

Gothic art was developed in western Europe from the second half of the 12th century to the end of the 15th century. The most characteristic Gothic building is the cathedral. Gothic architecture uses well-carved stone ashlars, and its essential elements include the arch. The thrust is transferred by means of external arches (flying buttresses) to external buttresses that end in pinnacles, which accentuates the verticality. The evolution of the flying buttresses should not only be considered as an aesthetic consideration, but also from a constructive point of view as an element of transmission of forces or loads. Thus, one evolves from a beam-type buttress to a simple arch, and finally to a rampant arch. In this work, we study the geometry of the rampant arch to determine which is the optimum from the constructive point of view. The optimum rampant arch obtained is the one with the common tangent to the two arches parallel to the slope line. A computer program was created to determine this optimal rampant arch by means of a numerical or graphical input. It was applied to several well-known and representative cases of Gothic art in France (church of Saint Urbain de Troyes) and Spain (Cathedral of Palma de Mallorca), establishing if they were designs of optimal rampant arches or not.

On the use of wooden beams as an anti-seismic device in stone masonry in Qasr el-Bint, Petra, Jordan

Timber string-courses have clearly been used to strengthen stone ashlar buildings in Petra, Jordan. These embedded beams, used as a form, held the brittle stone ashlars together, especially during earthquakes. In this study, tied and frictional surfaces were used to represent the interaction between the masonry blocks and the embedded wooden beams. Micro and macro modelling were used to evaluate the effect of using the embedded wooden beams on the integrity of the sandstone monument Qasr el-Bint. The traction-separation behaviour of the cohesive element was employed to model the mortar joints. A continuum, plastic-based, damage constitutive model (CDP) was used to represent the behaviour of the masonry walls. The results of these investigations demonstrated the role of the embedded wood string-courses as an anti-seismic device in reducing the shear stress of the stone masonry structure by up to 33%. The repairing and preserving of these beams that function as anti-seismic devices are needed to strengthen the structure against potential earthquakes.

SURVEY, HBIM AND CONSERVATION PLAN OF A MONUMENTAL BUILDING DAMAGED BY EARTHQUAKE

SURVEY, HBIM AND CONSERVATION PLAN OF A MONUMENTAL BUILDING DAMAGED BY EARTHQUAKE

Hydric dilatation of ignimbritic stones used in the churchof Santa Maria di Otti(Oschiri, northern Sardinia, Italy)

In the historical buildings of eastern Logudoro (northern Sardinia), as well as in large areas of western Sardinia, ignimbritic rocks are widely used for ashlars and architectural elements as architraves, pedestals, shafts and capitals of columns. The decay processes affecting these rocks cause a progressive disintegration of the stone ashlars, with loss of material by exfoliation and flaking that determine a progressive retraction of the external profile of the façade with obliteration of the decorative elements. New data on the linear dilatation due to water absorption of these volcanic rocks are presented in this study in order to contribute to the evaluation of the impact of hydric dilatation in the stone degradation. The relationships among linear hydric dilatation of ignimbritic samples and petrographic and mineralogical characteristics as well as physical properties (texture, welding degree, porosity) indicate that three lithotypes with different behaviour in the water absorption can be distinguished in the ignimbrite rocks used as building stones in the church of Santa Maria di Otti (Oschiri, northern Sardinia, Italy). Although the linear hydric dilatation of the ignimbrites is moderate to low, we suggest that hydric dilatation may be an additional factor in enhancing the decay of the stones of the Santa Maria di Otti church.

Structural utilization of wooden beams as anti-seismic and stabilising techniques in stone masonry in Qasr el-Bint, Petra, Jordan

Wood has clearly been used to strengthen stone ashlar buildings in the ancient monuments in Petra, Jordan. However, to date, no analysis has been made of how wood works from structural engineering point of view, especially during earthquakes. Wood was used in a form of flexible string-courses that held the brittle stone ashlars together. This study analyses how this technique increases the strength of buildings and to what extent it functions as an anti-seismic device. Conducting such study requires the multidisciplinary collaboration of scholars with knowledge of architecture, architectural history and structural engineering. The result of this analysis proved the role of the imbedded wooden beams as anti-seismic device in reducing the shear stress of the structure by up to 50%. Repairing and preserving these beams are to strengthen the structure against possible earthquakes. The simulation results showed that the monument under study; which is Qasr el-Bint, has survived moderate earthquakes because of these beams that functioned as anti-seismic devices, and can continue to do so if these beams are retrofitted and strengthened.

Photo Scanner 3D Survey for Monitoring Historical Monuments. the Case History of Porta Praetoria in Aosta

Accessibility to cultural heritage is one of the most important factors in cultural heritage preservation, as it assures knowledge, monitoring, Public Administration management and a wide interest on cultural heritage sites. Nowdays 3D surveys give the geometric basis for an effective artefact reconstruction but most of the times 3D data are not completely and deeply investigated to extract other useful information on historical monuments for their conservation and safeguard. The Cultural Heritage Superintendence of Aosta decided to run a time continual project of monitoring of the Praetorian Roman Gate with the collaboration of the ITABC, CNR of Italy. The Praetorian Roman Gate in Aosta, Italy, of Augustus ages, is one of the most well-known roman monumental gates, it is a double gate with three arches each side, 12 meters high, 20 meters wide, made of pudding stone ashlars, Badoglio, travertine, marble blocks and other stone insertion due to restorations between 1600 and 1950. In years 2000 a final restoration intervention brought the gate at the present state of art, within the frame of a restoration and conservation building site with the purpose of treat the different decay pathologies and conditions. A complete 3D geometric survey campaign has been the first step for the monitoring of the gate morphologic changes and decay progress in time. The main purpose is to collect both quantitative data, related to the geometry of the gate, and the qualitative data, related to the chromatic change on the surface due to the stone decay. The geometric data with colour information permits to associate materials and stone pathologies to chemical or mechanical actions and to understand and analyse superficial decay kinetics. The colours survey will also permit to directly locate on the 3D model areas of different stratigraphic units. The project aims to build a rigorous quantitative-qualitative database so to be uploaded into a GIS. The GIS will become the monitoring main means. Considering the huge dimension of the gate and its urban location a multi-scale approach has been considered. Controlled and free images have been taken from the ground and the top of the gate so to reconstruct all the walls and the upper cover. A topographic survey has been done so to be able to control and relate all the different acquisitions. It has been chosen a Photo Scanner 3D system. It is a photogrammetry-based survey technology for point clouds acquisition and 3D models configuration, from digital images processing. This technology allows to obtain point clouds (xyz coordinates) with RGB information and geometries at different levels of complexity by processing a number of images taken with a limited set of constraints, with the use of a simple acquisition equipment and through an image matching algorithm (ZScan, by Menci Software). Due to the high walls of the arch gates, the higher part has been surveyed with a remote controlled drone (UAV Unmanned Aerial Vehicle) with a digital camera on it, so to take pictures up to the maximum altitude and with different shooting angles ( 90 and 45 degree). This is a new technology which permits to survey inaccessible parts of a high monument with ease and accuracy, by collecting redundant pictures later bound together by an image block algorithm. This paper aims to present the survey experience architectural monuments trough the application of a trifocal quick photogrammetric system, in surveying at different scales and for different purposes.

Om Barbartemplets datering

Om Barbartemplets datering

Structural Surveying And Diagnosis Of TheCentral Market Of Valencia, Spain

This paper provides an overview of the structural problems of an important and significant historic building of Valencia city. This building could be ascribed to the Modernist style, though it is a rather late example. The metallic structure of the ground floor covers 7,200 square metres, defining a very simple plan in Latin cross shape. In the same architectural ensemble there are included several pavilions which belong to the eclecticist movement. The brick vaulted basement of the building, covering the same surface of the market is also very interesting. Although the building has been looked after its functional aspects, it has not been maintained from a structural and constructive point of view. This case study is presented to examine the application of non-destructive investigative techniques to historic buildings, without interfering in their every day use. INTRODUCTION The Central Market of Valencia was built between 1918 and 1929, based on the plans of a project dated 1914. It is a Modernist Style building, located on the site of a demolished abbey, within the historic area of the city. The polygonal perimeter adapts to the complex medieval urban layout (Fig. 1). The plan, of basilic design, is organised by means of two symmetrical axes, which are the arms of the Latin cross. The plan is completed by means of secondary bays, parallel to the longer bay. The Fish Market area, with an octagonal plan, is attached to one of the sides of the General Market area. In this way, the plan of the Transactions on the Built Environment vol 4, © 1993 WIT Press, www.witpress.com, ISSN 1743-3509 194 Structural Repair and Maintenance of Historical Buildings building adapts to the irregular shape of the site. Its height is respectful with the four storeyed buildings of the surroundings. The principal bays, coinciding with the arms of the cross are 107 and 51 metres long. The width of the central bays is 23.80 metres, and 13.60 metres for the secondary ones. The ground floor space is used for the daily retail market sale, and the basement, created for the wholesale of fish, is used at the moment as a parking area. There are two pavilions built in brick, on each side of the principal entrance of the Market, and another one attached to the opposite facade (Fig. 2). All these pavilions have an administrative use. This large and complex building maintains its original use. No maintenance works have been done on it, except those to provide the supplies which are necessary to develop the activity of daily market. Several damages have been detected on the walls and stone decorative elements, that we recommend should be studied. CONSTRUCTIVE DESCRIPTION The structure of the ground floor is made of metallic trusses, with riveted unions, separated from one another by 6.80 metres. A dome with a 14.00 metres diameter is located over the transept, being the keystone at 27.00 metres high. A square grid formed by depressed arches, defines the vaulted structure of the basement. The arches are supported by circular columns, made of moulded bricks. Tensile rods are embedded in the floor depth. Masonry is used for the foundations. The pentagonal shaped facades, are defined by means of stone ashlars. The facades are made of brick, dressed with stone up to the basement, and with decorated tiles up to the window sill. Big arched openings with metallic windows (3 or 5 depending on the width of the facade), are shut in its upper part with stained glass allowing the sales area to be illuminated by the sunlight, and with horizontal glass fittings in its lower part, to allow natural ventilation. The roofing, supported by means of metallic beams fixed between the trusses, is composed of prefabricated concrete slabs, 4 cm thick, and tiled with ceramic plane tiles. The vaults of the basement, formed by three sheets of bricks supports the floor of the sales area by means of brick walls of irregular height. Transactions on the Built Environment vol 4, © 1993 WIT Press, www.witpress.com, ISSN 1743-3509 Structural Repair and Maintenance of Historical Buildings 195