Reuse and structure in historical architecture. Constraints in the conservation project

The lack of use in historical architecture causes, over time, deterioration of materials and structures and, thus, loss of memory of the place and its meanings. A conservation that is based on the building history and 'compatible' with the architectural vocations represents a possible way to preserve the historical and architectural values and, therefore, their symbolic mean. The choice of a new use, while remaining a way to preserve and transmit the heritage to the future, has to deal with issues related to the structural safety, especially vertical loads and the actions caused by exceptional events such as earthquake. Especially in the last decade, the Italian legislation has developed specific rules for the cultural heritage, accepting in seismic zone interventions that 'improve' the structural behavior without reaching the levels of 'adaptation' of new buildings. However, the designer is required to calculate coefficients such as “categories environments (Cat.)” and “use classes (Cu)” – that depend on the type and degree of crowding and that affect entities loads and seismic actions. For the purposes of structural safety, the choice of the function covers a key role and the more the new use of the project is compatible with the history of the building loads, the less invasive and respectful of the natural conception of antique structures are the new interventions. The preservation of both the original structural elements and those added over time can also help to validate the memory of places, their functions and events happened in them. This will consequently keep even more the symbolic value of antique architecture. Concrete slabs were left exposed during the recent intervention in the Kongresshall (Nuremberg, Germany). Similarly, during the first restoration (after the Second World War) of the oratory of the Filippini (Bologna, Italy), a portion of wall was rebuilt in concrete and brickwork, and it remained intact in the intervention made in 1997. These are just a few examples that intend to highlight, through a conservation of existing structural elements and their direct contact with new structures, a close dialogue between history and architecture, past and present, memory and transmission to the future. The purpose of this paper is to think about the combination of safety and conservation, from the point of view of the reuse. It will draw inspiration from the case studies presented in the workshop and will also allow for a review of operational problems in the wider European framework. Additionally, Italian case studies will be accurately analyzed to review a wide range functional aspects. In every case, the analysis will be primarily focused on the trade-off between the reuse needs, on the one hand, and the architecture values and the structural logic of the building, on the other. This is the only way to guarantee the real purpose of conservation.