STRUCTURAL INTERVENTIONS ON MONUMENTAL BUILDINGS

Transcription

1 STRUCTURAL INTERVENTIONS ON MONUMENTAL BUILDINGS DOCTORAL THESIS (SUMMARY) DOCTORAL CANDIDATE: BULBUK MARTIN-ŞTEFAN SCIENTIFIC COORDINATOR: Prof. Dr. Eng. ILDIKÓ BUCUR The doctoral thesis deals with the topic of structural interventions on monumental buildings and is mainly based on a series of actual structural interventions of the author, on certain historic or architectural monuments of our national heritage. This experience is supported by deep theoretical studies and research. We all know that nowadays we emphasize the process of restoring and rehabilitating built heritage, as the most valuable component of the history of national, European and world culture. We must say that all interventions on monumental buildings are unique if we take into account the degree of deterioration of the structural subassemblies and the needs of functional rehabilitation of a particular objective. All structural interventions on monumental buildings must assure resistance and stability at least equal to the original one, or even higher, in order to acquire new and modern functions, asked by their further use for the benefit of the society. They also have to comply with well determined rules concerning their structural and architectural originality and authenticity. Assuring resistance and structural stability needs, acquiring new modern comfort functions, and maintaining authenticity as a whole and in details (regarding architecture, materials, or technologies) cause difficulties to specialized designers, as well as to execution engineers and specialists. However, given the extremely important cultural aim, the solution to technical problems until the fulfillment of the objective must weigh the same. 1

2 The present doctoral thesis follows the path of achieving this desideratum, the author hoping to help the specialists involved in the rehabilitation of monumental structures and contribute to the theory and practice of the process of saving built heritage. In order to provide the theoretical and normative framework necessary to the specialists in interventions on monumental structures, the author presents in the first chapter current status of historical structures conservation and PhD thesis objectives. The author further underlines the present trends and the opportunity of studying about structural interventions on monumental buildings. In the second chapter the author presents the theoretical bases and the doctrines of protecting built heritage. He presents the definitions and the main principles of monument protecting. He refers to the situation of national heritage, including cultural and historical settlements that need urgent interventions in order to be saved. Further on he presents the Romanian and international regulation in this respect and the list of the UNESCO world heritage in Romania Chapter three describes the general criteria of the built heritage conservation and rehabilitation. This chapter presents the rehabilitation expertise process and the general scheme of the stages of rehabilitation of historical structures. The author also presents the rehabilitation-endurance binomial, which has to be permanently under the specialist s attention during design and execution. He enumerates and presents preservation methods. Chapter four presents a historical retrospective of the relation function-formstructure, as well as the influence of the technical development on the evolution of masonry and cast structures. Doctoral thesis presents binders used in historic structures - it has some recipes recommended. The fifth chapter is a description and classification of the types of masonry according to the structural subassemblies they are part of. The author insists on horizontal subassemblies, namely historic masonry floors and vaults, as well as on their execution technologies and the used binders. He further presents the characteristic damages and deficiencies of masonry vaults, as well as the most important consolidation solutions applied to these structures. Here are some of them: metallic tie-rods reinforced covering, joining girders of reinforced concrete or steel and the system of embedded steel spirals (Brutt-Saver). 2

3 The thesis proposed developing a method for determination the technical state of historical buildings constructed on 1 4 levels, the structure of resistance, mainly masonry. For a fair decision for the rehabilitation of a building is required as objective and rigorous assessment of the technical state. The methodology aims to quantify the technical state of the building. Determination of the technical state is performed using quality indicators based on decay tables, prepared by the author. The method is general, with the possibility to adapt to any type of construction, assembly or subassemblies. In Chapter six the author presents the general issues of structural interventions concerning functionality and structural reliability, as well as the specific issues for historic buildings, that of authenticity and adaptation to modern demands. The author presents a classification of the structural interventions according to the degree of intervention on the original structure. It is presented and exemplified in the Tables : consolidation interventions without modifying the original structure; consolidations that modify the structure, but use structural elements compatible with the original structure; indirect consolidations, using additional structural elements or subassemblies, but preserving the originality of the structural form; structures in the case of which modern functional necessities impose adding new buildings, which will be integrated as well as possible in the ancient whole. In this chapter the author also presents 6 case studies of consolidation and rehabilitation, executed by him. The consolidation and rehabilitation solutions are described in details and accompanied by pictures taken on the site during execution. Every single case presents a new constructive solution, which may serve to solve similar cases in the future. The consolidations of masonry vaults, by taking over the dead and service load by an additional floor executed above them, may allow maintaining the original vaults and saving the possible mural paintings on them. Consolidating wooden floors by drawing them back to their original positions using special technologies, without demolition and reconstruction, as well as consolidating the buildings they are part of is an approach that may save important and imposing monumental buildings from being destroyed or replaced by new fake constructions. 3

4 Table 6.1 Strengthening, preserving the original structure. Case Masonry vaulted structure Theater of Turda, Romania [ Deficiency Precarious technical state of the masonry pillars and arches of the basement Masonry vaults Orăştie, Romania [ Cracks on the masonry vaults and arches Covering with reinforced concrete using Pozzolanic cement Alternative solution of strengthening Bohemian brick vaults Cracking of the arches and vaults Brutt Saver system: embedded steel spirals fixed with special mortar 4 Strengthening solution Partial covering with reinforced concrete using Pozzolanic cement

5 Table 6.2 Strengthening, adding compatible structural elements Case Deficiency Strengthening solution Arch and vault structures Horizontal displacement of the supporting structural element Metallic tie-rods of convenient type Multi-storied building masonry Lateral displacements of the external walls, damage of the elevation wall Joining girder at the level of the slab and foundation Mine railway bridge Continous beam of reinforced concrete Bălan, jud. Harghita Unacceptable vertical deflections and cracks in the middle of the span Strengthening with special tie-bar system 5

6 Table 6.3 Indirect strengthening providing additional bearing structure Case Deficiency Strengthening solution Saint Michel Church, Cluj Insufficient lateral stiffness of the The Gothic vaults are hung on a The Gothic vaults of the supporting walls, lateral supplementary slab system lying on sanctuary displacements the perimeter walls Masonry arches and vaults Basement of Theater, Turda Precarious technical state of the masonry Composite slab of reinforced concrete and steel deck on metallic beams Masonry vaults, basement of the Palace of Justice, Odorheiu-Secuiesc Cracks and breaks, detached bricks, important vertical displacements Additional reinforced concrete slab on metallic beams Timber slab with ornamental ceiling, Palace of Justice, Odorheiu- Sec. Great and evolutive deflection of the slab, cracks in the ornamental plastering of the ceiling Lifting girder of reinforced concrete with its additional supporting timber structure 6

7 Table 6.4 Rehabilitation by adding new blocks to the building, functional improvement Case Palace of Justice, Odorheiu-Secuiesc New staircase of reinforced concrete, steel and glass Emplacement of the new block of the staircase between two old blocks of the building Interior view ortotrop staircase According to the author it is necessary to know the architectural styles, as well as structures, materials and technologies used in the past and at present in order for the specialist to be able to distinguish among the different historical steps of certain structures or buildings, which were built successively in different styles, with different characteristics. The consolidation of historical slab structures and the reparatory reconstruction, with original materials, of the vaults of monumental buildings, by the original applied technologies, are important achievements that may serve as examples for further similar interventions in the case of other building with similar deficiencies. Chapter seven is a Guide of structural consolidations on monumental buildings prepared by the author - containing recommendations concerning structural interventions. This guide is drafted for those involved in the process of rehabilitation and structural consolidation of monumental buildings. It describes all the steps that have to be passed in order to achieve a successful rehabilitation. The guide contains a series of recommendations necessary to executants, regarding structural interventions. It offers a methodology of identifying historic buildings by tables containing the building characteristics for the Gothic, Baroque and Eclectic era. Further on, the guide presents in details the necessary and compulsory achievement steps of the rehabilitation process of the buildings on the construction site. 7

8 Chapter eight contains some conclusion of the author about the importance of the professional treatment concerning the built heritage. Chapter nine contains mentions about the author s original contributions. They consist mainly in: theoretical contributions concerning the examination and determination of the technical state of the historic structures; innovative techniques and technologies for rehabilitation of assemblies and subassemblies of historic constructions; the guide of structural consolidations on monumental buildings and technical recommendations for structural interventions, based on the experience gained throughout the execution years spent on our country s construction sites, regarding structural interventions to monumental buildings. Eng. Stefan-Martin Bulbuk 8