Abstract
Abstract. The recovery and retrofitting techniques adopted for historical structures and archaeological sites face an apparent dichotomy between conservation of constructions and the safety of users. Literatures show several examples where the current day structural safety of historical constructions, gets defined by the nature of past interventions, the compatibility of materials and elements used in retrofitting. The adopted interventions were, in their time, considered innovative, but over the years their compatibility and reversibility leave the historic constructions structurally vulnerable. For these reasons, a careful understanding of the structural systems is fundamental for the implementation of appropriate retrofitting solutions. Especially for monuments and Archaeological sites the objective to be achieved has to be clear, avoiding destructive investigation tests. In this work the instabilities caused by a consolidation intervention on some travertine columns in a sector of the Flavian Amphitheatre, better known as “Colosseum” in Rome, are critically analysed. The current consolidation operations are compared to the previous one. The restoration activity involves in-depth diagnosis process: the historical analysis of the failures and restorations of that area of the Colosseum, a survey of the crack pattern and an indirect investigation on the travertine of the columns. Subsequently the various data coming from the knowledge phase are elaborated, in order to have a correct interpretation of the causes triggering the failure and guide the choice of the most correct retrofitting techniques.
Highlights
The knowledge of construction and retrofit techniques, analysed in their historical context, as well their failure mechanisms, is a prerequisite for the protection of monumental buildings and assumes a fundamental role in determining the damages and for planning the retrofit interventions (Giuffré, 1993).In this sense, the consolidation interventions adopted mirror the technical knowledge of their respective periods
The geometrical and technological survey of the façade showed a crack pattern defined by vertical cracks in the column of the second floor, passing through the holes, in which the rebars were inserted in the retrofit intervention of 1978-1979
The analyses performed in the field of the fracture mechanics (Kirsch, 1898), (Andreeva et al, 2014), suggested that the vertical cracks were caused by the presence of a radial force inside the rebars’ holes (Romis, 2010)
Summary
The knowledge of construction and retrofit techniques, analysed in their historical context, as well their failure mechanisms, is a prerequisite for the protection of monumental buildings and assumes a fundamental role in determining the damages and for planning the retrofit interventions (Giuffré, 1993).In this sense, the consolidation interventions adopted mirror the technical knowledge of their respective periods. The main problem in those cases, given the limited computational possibilities, was the desire to make the structure similar to the calculation model, incompatible materials were introduced for the structure strengthening (D’Altri et al, 2019). This aspect is even more critical in case of monumental buildings or archaeological sites, where even the modifications and the changes occurred during the centuries are difficult to detect, because involve the superposition of different materials and construction technologies, the alteration of the structural homogeneity and the differences in realization respect to the original design. The structural safety is, influenced by the conservation of the architectural profile and morphology of the structure
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