The Roman Temple in Évora: a Conservation Proposal. Giulia Grecchi, Alex McCall, Jungtae Noh, Evan Speer, Mohammed Tohidi. - PDF

Title: The Roman Temple in Évora: a Conservation Proposal Author(s): Unit: Giulia Grecchi, Alex McCall, Jungtae Noh, Evan Speer, Mohammed Tohidi. SA7 Institution: UNIVERSITY OF MINHO Date: March 23 rd,

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Title: The Roman Temple in Évora: a Conservation Proposal Author(s): Unit: Giulia Grecchi, Alex McCall, Jungtae Noh, Evan Speer, Mohammed Tohidi. SA7 Institution: UNIVERSITY OF MINHO Date: March 23 rd, 2012 Erasmus Mundus Programme: ADVANCED MASTERS IN STRUCTURAL ANALYSIS OF MONUMENTS AND HISTORICAL CONSTRUCTIONS Consortium Institutions: UNIVERSITY OF MINHO, PORTUGAL CZECH TECHNICAL UNIVERSITY IN PRAGUE, CZECH REPUBLIC UNIVERSITY OF PADOVA, ITALY TECHNICAL UNIVERSITY OF CATALONIA, SPAIN Satellite Participant: INSTITUTE OF THEORETICAL AND APPLIED MECHANICS, CZECH REPUBLIC TABLE OF CONTENTS Table of Contents... 1 List of Figures Introduction The city of Évora The Roman Temple Name, Geometry and Materials History Initial Site Survey Damage Survey Biological colonization Geometric Survey Ground Penetrating Radar Investigation Dynamic Identification Limit Analysis Dynamic Analysis Discrete Element Analysis Numerical Model Construction Model Calibration Dynamic Input Failure Mechanism Local failure mechanism of a single free standing column Global Failure Mechanism Failure Mechanism Conclusions Intervention Discussion Strengthening Proposals Alternative proposal Chosen Strengthening Proposal Cable Intervention Verification Strengthening Proposal Pricing Conclusions Acknowledgements LIST OF FIGURES Figure 1-1 The Roman Temple in its current state... 4 Figure 2-1 City Plan (El Templo Romano de Evora, T. Haushild)... 5 Figure 3-1 Graphic reconstruction (http://temploévora 6 Figure 3-2 Temple visual 1795 (Estudios Diversos)... 7 Figure 3-3 Iron connection between beams... 8 Figure 4-1 Example of damage in a capital... 9 Figure 4-2 Example of damage in one of the central column... 9 Figure 4-3 Example of damage in the base of a column... 9 Figure 4-4 Schematic showing loss of column section Figure 4-5 Base separation Figure 4-6 Front façade damage Figure 4-7 Biological colonization of the capital Figure 4-8 Biological colonization of column Figure 4-9 Biological colonization of base Figure 4-10 Front Façade Biological Colonization Figure 5-1 3D Scan laser point cloud Figure 5-2 Column Leaning (left) and Joint Interface Geometry For 3DEC Input (right) Figure 7-1 Dynamic Identification Results of Column E Figure 9-1 Elastic Spectra Figure 9-2 Accelerogram (Type 2 filtered) Figure 9-3 Post Filtering Comparison of Artificial vs Code Spectra Figure 9-4 Velocity histogram of the near field earthquake Figure 9-5 Failure mechanism of free standing columns by horizontal ground motion, Figure 9-6 Displacement responses of the top block by ground motion in x, y, z- direction, PGA multiplier factor 2, k n =3490 GPa/m Figure 9-7 Max displacement of the top of freestanding column by ground motion Figure 9-8 Maximum displacement of the top with varying joint stiffness properties Figure 9-9 The Complete Temple Model with Monitoring Positions Figure 9-10 Global response of temple (X-direction): (a) PGA multiplier factor 7, (b) PGA multiplier factor Figure 10-1 East side: reinforced glass strengthening Figure 10-2 Maximum displacement responses of the strengthened free standing column Figure 10-3 PGA multiplier factor of Figure 10-4 PGA multiplier factor of Figure 10-5 PGA multiplier factor of 2 for the complete model (position 23) Figure 10-6: PGA multiplier factor of 2 to the complete model (position 20) Figure 10-7 PGA multiplier factor of 2 to the complete model (position 17) ANNEXES Annex A: Visual inspection on columns Annex B: Visual inspection on architrave Annex C: Damage and Biological growth maps Annex D: GPR results Annex E: Accelerometer maps setups Annex F: Geometry & intervention Annex G: Block2D results Annex I: Prices 3 1. INTRODUCTION The Roman Temple of Évora is located in the historic city center of Évora, Portugal. The temple dates back to the 1 st century AD and was classified as a national monument in The temple has undergone numerous changes throughout history. In its current condition (Figure 1-1), fourteen columns remain, twelve of which include capitals and support a beam system. Several archeological studies and excavations have been carried out on the temple. However, the temple has never been structurally analyzed. The structure s seismic resistance is of particular concern. The temple is located in a region subjected to a moderate seismic hazard, with a peak ground acceleration (PGA) of 0.11 g. Therefore the main purpose of this report is to ascertain the temple s behavior under seismic excitation. It was proposed that the structure be analyzed using limit analysis and discrete element dynamic analysis. For the purpose of the analysis the structure is assumed to be composed of rigid blocks with dry joints. The numerical models will be based on geometric information obtained from a recent 3D laser scan. The results of the analysis of the temple will then be presented and discussed in detail. Furthermore, the requirement of strengthening works to ensure the seismic safety of the temple will also be thoroughly investigated. All works will conform with the guidelines and framework of the ICOMOS charter. The work of this project was made possible through collaboration with the Regional Directorate of Culture (DRC) of Alentejo. Figure 1-1 The Roman Temple in its current state 4 2. THE CITY OF ÉVORA The city of Évora is the capital of the Alentejo Province in the south of Portugal. The city is approximately half way between the Portuguese capital of Lisbon and the border with Spain to the East. Évora is thought to date back to the Celtic times. In 57 BC, the city was conquered by the Romans who renamed the city Liberalitas Julia. Signs of the Roman presence are still evident today (e.g. the baths and the Cardo and Decumano roads, Figure 2-1). The city was also occupied by the Visigoths during the 5 th century and by the Moorish after 1165, however the majority of the city is medieval. Most notably, the medieval age is represented by the cathedral believed to have been constructed between the 11 th and 14 th centuries. Évora was also a residence for the royal family in the 15 th century. During the 16 th century, many urban planning works were undertaken, including the Agua da Prata aqueduct built between 1531 and 1537 by Francisco de Arruda and many fountains. Some fountains still remain, most notably those in Praça do Geraldo. Moreover, in that period Évora started to be influenced by Jesuits, who taught at the University of Holy Spirit between 1553 and 1759 when they were expelled by the Minister Pombal. Évora then began to rapidly decline. The town of Évora is still very well known for its historical monuments and as such has achieved UNESCO World Heritage status. Decumano (E-W) Cardo (N-S) Figure 2-1 City Plan (El Templo Romano de Evora, T. Haushild) 3. THE ROMAN TEMPLE 3.1. Name, Geometry and Materials The remains of the temple consist of 14 hexastyle columns approximately 0.9 m in diameter. Originally, there were 32 columns in a peripteros layout. The columns sit on a podium 3.5 m high, 15 m wide and 25 m long. Since the column drum heights vary and are not consistent throughout the 5 structure, it is understood that the columns were originally covered in stucco to hide the imperfections. More recently, however, this stucco was misunderstood as an intervention measure and removed. For a long period of time, the temple was known as the Diana Temple, as it was thought to be dedicated to the goddess Diana. However, this is now believed to be untrue and that the temple was actually built in honor of Emperor Augustus. The Roman Temple of Évora has two sibling temples on the Iberian Peninsula, one in Barcelona and one in Merida. It is surprising that the temples are so well preserved, and there are two theories which may explain this. First, the temples are a long distance from Rome, therefore they were preserved to show devotion to Roman. Alternatively, it s also thought that the temples are in good condition because they are compared to buildings in Rome which have not been preserved to the same standard because there are so many. The stone used to construct the temple has previously been analyzed by Lopes et al. using a petrographic technique. The analysis concluded that the columns and architrave are of local granite and the capitals and base of marble from nearby Estremoz. Studies have also revealed the presence of water channels on three sides of the building. A lot of conjecture still remains around the layout of the temple and the position of the staircase. It has been thought that the staircase may have been orientated as shown in Figure Errore. L'origine riferimento non è stata trovata.. Alternatively, the staircase may have run parallel to the front of the building or there may have been a combination of both layouts. Archaeologists are still debating this topic, as there is not conclusive evidence of any of the layouts History Figure 3-1 Graphic reconstruction (http://temploévora Construction of the temple began in the 1 st century AD during the time of Emperor Augustus in the Forum of Liberalitas Julia (Évora) and was finished between the 2 nd and 3 rd centuries. It is understood that the temple was at least partly destroyed by the Visigoths during the 5 th century. During the 14 th century, walls were constructed between the outer columns and the temple was then 6 linked to the Évora castle and used as the tower between the 14 th and 18 th centuries. One of the most recent uses of the temple was as a butcher s shop. As late as the 19 th century, pyramid shaped merlons could also still be seen at the heads of the outer walls, as can be observed in Figure 3-2, where the temple is shown as it was before Cinatti s restoration. Figure 3-2 Temple visual 1795 (Estudios Diversos) Between 1870 and 1871, considerable intervention was carried out on the temple by Giuseppe Cinatti. Generally Cinatti was a follower of Violet Le-Duc s theories on intervention but in the case of the Évora temple, he seems to have followed Ruskin s intervention theory of allowing the structure to naturally deteriorate. It has been thought that the main reason pushing Cinatti not to reconstruct was that it was not possible for the original function of being a pagan temple to be restored and reused. Therefore, it was decided to re-create the ruin and give residents and visitors an insight into the Roman history of Évora. Rather than reconstructing the pagan temple, the walls (which had been added between the columns) were removed. Although the walls added between columns were not original, it is quite certain that they helped to ensure the survival of the temple, most notably through the Lisbon earthquake of An inventory was made of missing sections of the temple, the podium was surveyed and inspected, and some beam sections were connected with iron ties for safety, as seen in Figure 3-3. A section of frieze found in the city hall was also returned to the temple and the entire temple underwent a cleaning regiment. Furthermore, the plaza around the podium was paved, and a metallic barrier was fixed at one end of the temple to prevent people from entering the podium. By only cleaning the structure and not reconstructing, Cinatti knew that the work could be completed in a short period of time. He had come from Lisbon where considerable restoration works were being carried out on the Monastery of Jerónimos. These works were, however, very time consuming. Once the intervention was complete, a decree was passed forbidding the removal of any pieces of the temple. The decree appeared not to have been successful, given that only part of the temple remains. 7 It is understood that a marble base from one of the columns was used as a table in a local church and a drum from one of the columns was being used to crush wine to make grapes in a local farm, however its unknown whether these were removed before or after the decree was passed. It s also thought that a number of the pieces of the temple are being used in the gardens of residents of Évora, who are unwilling to return them through fear of being accused of stealing. After the intervention of the temple, the city also underwent a period of renovation in its urban plan. Some monuments without any historical value were demolished and others were restored, such as the Cathedral and the Church of Saint Francisco. Figure 3-3 Iron connection between beams 8 4. INITIAL SITE SURVEY On October 31 st, 2011, a site survey was carried out to determine the current condition of the temple. Primarily the purpose of this survey was to identify structural damage and biological colonization Damage Survey The damage survey carried out during the initial site survey was a visual inspection to identify cracks and loss of section to structural elements (see Figure 4-1, Figure 4-2, Figure 4-3). The information from this survey could produce a better understanding of the structure and could then be used when modeling the structure for the structural safety assessment. The severity and location of all damage was recorded on elevation drawings of the temple. Figure 4-1 Example of damage in a capital Figure 4-3 Example of damage in the base of a column Figure 4-2 Example of damage in one of the central column Throughout the temple, most of the components are affected, including column bases, drums, and capitals. The most damaged area of the temple are the two middle columns in the front façade, which have been subjected to a considerable loss of section. These columns were designated A3 and A4 in 9 the identification grid found in Annex F. It is understood that sections of the column had been cut to install a door, as seen in Figure 4-2 and Figure 4-3. It is possible that this loss of section may lead to kinematic behavior of the blocks. The reduced areas in the drums were recorded, and included in the structural model. Figure 4-4 Schematic showing loss of column section Some of the bases, which were constructed from marble, have also been badly damaged. In some cases, this includes possible complete separation as shown in Figure 4-5. At the time of the first inspection, it was not possible to examine the capitals in any detail. Therefore, this inspection will be carried out in a future inspection. Figure 4-5 Base separation Damage maps prepared from the inspection are presented, showing the extent and location of damage. Damage maps for the front façade can be seen in Figure 4-6Errore. L'origine riferimento non è stata trovata.. For the entire collection of damage survey figures, see Annex C. The damage maps created are strictly qualitative, showing general severity and scope of the damage present in the structure. The maps produced were overlaid on the only structural drawings present at the time of the survey. Therefore, measurements and elevations are not meant to be extracted from these drawings. 10 4.2. Biological colonization Figure 4-6 Front façade damage A visual inspection was also made to determine the degree of biological colonization. Mainly, this is a result of the growth of lichen, algae, and moss, which is easily visible throughout the temple (see Figure 4-7, Figure 4-8, Figure 4-9). The most severely affected areas are the bases of the columns which exhibit a range of moss and fungus growth. However, due to the lighter color of marble compared to the granite, biological growth on the capitals and bases is more obvious. Due to lack of time, no identification on the type of biological growth was carried out. It is known that one of the marble base has been cleaned with Laser, but it still to be understand if this is good for the structure. Maps were also created to show the extent of the biological colonization on the structure, as seen on the front façade in Figure The entire set of biological colonization maps can be seen in Annex C. As with the damage maps created and described before, the biological colonization maps are strictly qualitative, showing general severity and scope of the colonization present in the structure. 11 Figure 4-7 Biological colonization of the capital Figure 4-9 Biological colonization of base Figure 4-8 Biological colonization of column Figure 4-10 Front Façade Biological Colonization 12 5. GEOMETRIC SURVEY There is a multitude of various methods for surveying the geometry of historical buildings. Deteriorations and ornaments, however, can make this process much more difficult and time consuming. The use of simple surveying instruments is not always possible to make accurate maps. Accurate plans and drawings have a very important role in every part of the investigation process. Upon commencing this current project on the Roman Temple, AutoCAD drawings and 3D scan laser data of the temple were provided. One of the firsts tasks of the first site visit was to verify the accuracy of the provided AutoCAD drawings. After comparing in situ measures with the AutoCAD drawings, it was realized that the drawings were not accurate. The drawings did not take into account leaning, rotation, loss of section, deterioration of material, cracking, and the actual geometry of the individual column drum elements. Since the drawings were not accurate and not all the necessary tools to obtain all the measurements of the structure were available, it was decided to use the 3D scan laser data to measure and draw details that were needed, including leaning of columns and other inaccessible parts. The 3D point cloud from one of the 3D scans can be seen below in Figure 5-1. Figures detailing the entire geometric survey can be seen in Annex F. Figure 5-1 3D Scan laser point cloud Since the 3D scan data files are really heavy for a normal laptop, some problems were faced extracting useful information. To access all the features of the 3D scan files, a specialized software was needed. Through collaboration with Dr. Luis Mateus of the Architecture department at the Technical University of Lisbon, all the useful information were extracted from the 3D scans and sections of the structure (both vertical and horizontal) at intervals of 5 cm were obtained. These files allowed the preparation of accurate maps which include the measures of inaccessible parts, the leaning of the columns (Figure Figure 5-2 Column Leaning (left) and Joint Interface Geometry For 3DEC Input (right)) and other useful information needed to properly build the models. 13 Figure 5-2 Column Leaning (left) and Joint Interface Geometry For 3DEC Input (right) The data obtained was integral to the construction of accurate geometries to input into the static limit analysis and dynamic discrete element analysis. In this way, leaning, variations in element diameter and size, loss of sectional area, and split elements could be modeled using the 3DEC discrete element software. 6. GROUND PENETRATING RADAR INVESTIGATION During the second visit to the temple, it was possible to perform Ground Penetrating Radar (GPR) testing with the help of Dr. Francisco Fernandes. Maps and extended results are collected in the Annex D. From GPR investigation, it was understand that there are no connectors between column drums, but, steel connectors were detected between several architraves. We could not survey all the joints on the architraves due to lack of time, but we assume that most of the architraves beams are connected through casted steel elements. It was also possible to observe holes in stones from the pavement and a small focused investigation lead to the conclusion that the stone elements around the temple are, most likely, interlocked through some connected elements. 7. DYNAMIC IDENTIFICATION During the second site visit in January 2012, dynamic identification tests were conducted over a period of two days. The tests involved the placement of 12 independent accelerometers throughout the structure in 5 different configurations. Two tests have been carried out for each configuration: the first test
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