Structural reinforcement and conservation on tufa historical buildings

The article compares two reinforcement systems applied to a building made of tufa masonry: a traditional reinforced plaster made of electrowelded mesh and concrete on one side and a low-thickness reinforced plaster using composite materials and cement-free mortar. Some reversibility tests carried out on a building’s tufa in the center of Naples have highlighted the advantages of using composite materials in the context of a restoration site, where the principles of justice reflect the characteristics of compatibility, reversibility, durability and poor invasiveness.

The issue of seismic vulnerability of protected historic buildings in Italy is highly relevant, following the series of seismic events that have caused destruction and irreparable damage to the historical and architectural heritage in recent years. The apparent, but sometimes substantial, opposition between the themes of conservation of the building and those of safety (not only for people but also for the survival of the asset itself) has led to extreme positions and a fundamental immobility that certainly did not benefit an already critical situation. In any case, the search for new solutions, compatible with the principles of conservation but still ensuring an acceptable level of protection, continues and becomes increasingly targeted and articulated with diverse proposals, sometimes supported by scientific evidence, and others particularly daring.

The majority of existing constructions in the historic centers of Italian and European cities are made of ordinary brick or stone masonry. Depending on the size and shape of the elements, their origin, the type of block, and the quality of the mortar, various masonry textures can be found.

Frequently, these buildings have multiple leaf walls, with or without effective connections between them. Under seismic actions, the vertical walls are subjected to high horizontal actions in-plane (shear) and out-of-plane (flexure). The shear strength of the masonry walls in existing buildings is limited, so the resistance capacity to an earthquake is inherently linked to the collapse due to shear of the masonry units and floor bands. Additionally, the horizontal action can cause partial collapses due to the activation of various out-of-plane mechanisms involving the rigid movement of masonry elements. Currently, as stated in Chapter 8 of the Ministerial Decree of 14/1/2008, there are multiple reinforcement techniques available, such as the insertion of steel or composite material tie rods, which have proven to be effective reinforcement techniques. […]