Historic Construction and Conservation

Materials, Systems and Damage

Pere Roca, Paulo B. Lourenço, Angelo Gaetani

• Publisher: Routledge
• Year: 2019
• ISBN:
  9780429628054
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Construction & Architectural Engineering
• Index: Technology & Engineering

Conservation in the built environment raises fundamental questions which have been debated for centuries - what is worth preserving, how is it possible, why is it important?

This book takes a modern approach to the meaning of a heritage structure and its conservation. The historical evolution of conservation is briefly addressed, considering prominent individuals and cases; along with the history of construction, focusing on materials and related structural elements, with insight on the sizing rules adopted by masons. This explains structural decisions made during the construction process and allows comparison of scientific theories from the 18th century to modern understanding of limit analysis. Damage and collapse mechanisms for masonry construction, as the most widespread structural form for historical buildings, is described. Excess permanent loading and settlement is differentiated from environmental and anthropogenic actions such as earthquake or incorrect intervention.

The team of authors brings together unique expertise, with high level research and leading practice with archetypical cases from around the world. The book addresses the history of conservation by exploring materials and structures and the history of construction and damage, so it is of value to students and professionals in civil engineering and architecture, as well as archaeologists and art historians.

Chapter 1

Modern understanding of conservation and of heritage structures

Among the many reasons, the study of historical buildings causes an everlasting sense of wonder due to the experience of being united with the outstanding achievements of the past, feeling and learning to appreciate ancient accomplished wisdom and pioneering technology. Due to the high value attributed to historical buildings today, our modern societies are dedicating a significant effort to their interpretation and conservation. In modern times, cultural heritage has received a strong scientific attention, and today, the approach to conservation is outlined by international charters and recommendations. After centuries of debates and still ongoing discussions, cultural heritage is universally recognized as a global wealth, whose conservation preserves local and universal cultural values and contributes to human development. In this regard, the respect for authenticity represents not only one of the highest goals of conservation, but it is itself the clue to understand conservation aims, purposes, appropriate methods and expected results. With this goal, the present chapter introduces the main aspects related to the modern understanding of conservation, starting from the definition of cultural heritage buildings and ending in heritage management.

As part of the cultural heritage, this chapter is also devoted to the modern approach and conservation criteria of historical structures. The need of preserving the structure and its static model are concepts relatively recent in the history of conservation, addressed to a great extent after the Second World War. An important breakthrough was the symposium held in Ravello, Italy, in 1995, whose outcomes are the basis of the ISCARSAH recommendations for the analysis, conservation and structural restoration of architectural heritage. ISCARSAH is the International Scientific Committee on the Analysis and Restoration of Structures of Architectural Heritage, and it was founded by ICOMOS (International Council on Monuments and Sites) in 1996 as a forum and network of engineers and architects involved in the conservation and care of the built cultural heritage. The last part of this chapter is devoted to the description of ISCARSAH Principles and Guidelines.

Finally, although punctual references are reported within the text, for further details, the reader is referred to the original charters, available online, for example www.icomos.org or whc.unesco.org. For a glossary of terms inherent to history and culture, the reader can visit www.pc.gc.ca/en/culture/dfhd/glossaire-glossary.

1.1 DEFINITION OF BUILT CULTURAL HERITAGE AND CONSERVATION

According to the United Nations Educational, Scientific and Cultural Organization (UNESCO, 1972), ‘cultural heritage’ is defined as follows:

• monuments: architectural works, works of monumental sculpture and painting, elements or structures of an archaeological nature, inscriptions, cave dwellings and combinations of features, which are of outstanding universal value from the point of view of history, art or science (Figure 1.1a);
• groups of buildings: groups of separate or connected buildings which, because of their architecture, their homogeneity or their place in the landscape, are of outstanding universal value from the point of view of history, art or science (Figure 1.1b);
• sites: works of man or the combined works of nature and man, and areas including archaeological sites which are of outstanding universal value from the historical, aesthetic, ethnological or anthropological point of view (Figure 1.1c).

These three groups are often referred to as architectural heritage, even if the designation built cultural heritage (sometimes cultural heritage buildings is also used) is more neutral and should be preferred. As it is possible to notice, according to the Venice Charter (ICOMOS, 1964), the definition of historic monument embraces not only the single built heritage work but also the urban or rural setting in which the evidence of a particular civilization, a significant development or a historic event is found. This applies not only to great works of art but also to more modest works of the past which have acquired cultural significance with the passage of time.

According to previous descriptions, it is also possible to enumerate other subclasses of built cultural heritage, namely, modern heritage and industrial heritage. The former concerns the heritage of architecture, town planning and landscape design of the modern era, that is, 19th and 20th centuries; the latter refers to the physical remains of the history of technology and industry, such as manufacturing and mining sites, as well as power and transportation infrastructure. Two examples are shown in Figure 1.2.

Figure 1.1 Examples of built cultural heritage. (a) Religious architecture, (b) historical urban texture in ancient city centres and (c) archaeological architectural remains.

Figure 1.2 Examples of modern heritage and industrial heritage. (a) Construction in masonry, steel and concrete, and (b) masonry chimney.

Regarding conservation, a general and structure-oriented definition is according to

• Nara Charter, all efforts designed to understand cultural heritage, know its history and meaning, ensure its material safeguard and, as required, its presentation, restoration and enhancement (ICOMOS, 1994);
• International Organization for Standardization, all actions or processes that are aimed at safeguarding the character-defining elements of a cultural resource so as to retain its heritage value and extend its physical life (ISO 13822:2010, Annex I on Heritage Structures.

For the sake of clarity, two other definitions are given:

• Preservation: action or process of protecting, maintaining and/or stabilizing the existing materials, form and integrity of a cultural resource or of an individual component, while protecting its heritage value. Note that preservation is much used in American English, while conservation is much used in European English for the same concept. In Europe, preservation is used more in the context of materials or conservators (such as stone, paper, textiles, paintings, sculptures and alike), whereas conservation is almost exclusively used for the built cultural heritage;
• Restoration: action or process of accurately revealing, recovering or representing the state of a cultural resource or of an individual component, as it appeared in a particular period of its history, while protecting its heritage value.

Note that restoration of a cultural heritage building is a controversial concept. It encompasses, in fact, many different interpretations, ranging between reconstruction and full ‘re-establishment’ (i.e. full recovery of an ancient building to its highest splendour, even involving the reconstruction of parts historically collapsed or possibly never built), to minimal intervention oriented to strict conservation. In this regard, it is worth noticing that a certain understanding of restoration (especially those connected to reconstruction and re-establishment) are out-of-fashion and in contradiction with modern conservation principles. Even if the word has a common root in Latin (restauro or to ‘restore, rebuild, re-establish, renew’), its adaptation to different languages entails also different perceptions. As an example, restauro in Italian, per the Italian Dictionary from Corriere della Sera, one of Italy’s oldest newspapers, reads ‘Operazione e procedimento tecnico che ha lo scopo di riportare in uno stato di buona conservazione e leggibilità un bene culturale e artistico’ or ‘Operations and technical procedure that aims to bring back a cultural and artistic asset to a state of good conservation and understanding’, for which the best European English translation would be conservation.

1.2 CULTURAL ...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• List of Figures
• List of Tables
• Preface
• Foreword
• 1 Modern understanding of conservation and of heritage structures
• 2 History of conservation
• 3 Construction materials and main structural elements
• 4 Vaulted structures in history and modern structural solutions
• 5 Ancient sizing rules and limit analysis of masonry arches
• 6 Damage and collapse mechanisms in masonry buildings
• Conclusions
• Bibliography
• Permissions
• Index
• Index of Monuments
• Index of Scholars