The reinforcement and seismic improvement of a building using the CRM Ri-Struttura system

The complex consists of multiple adjacent buildings arranged to form a square courtyard, with an additional architectural element. The intervention for the creation of the Museum Hub involves four buildings identified as Bodies A, B, C, and D, each consisting of 3 above-ground floors.

The masonry structures, which have been modified and integrated over time, now appear as a combination of elements with different construction characteristics. The horizontal elements in the various buildings range from barrel vaults to wooden, composite concrete, and steel and tile floors.

Characteristics of the vertical elements: The vertical elements are mainly composed of load-bearing masonry walls, but there are also internally framed structures made of steel and reinforced concrete. Specifically:

• The load-bearing structures consist of stone masonry with solid brick inserts laid with lime mortar. The texture of the masonry appears somewhat disorderly in certain parts of the building, especially regarding the thickness of the elements. A significant characteristic is the considerable thickness in the lower levels (an average thickness of approximately 1.10m on the first floor), which tapers off towards higher floors (about 1.00m on the mezzanine floor and 0.90m on the first floor).
• Some steel frame structures with HEA 400 profiles are present in the western section as an encasement intervention. They currently serve as the supporting element for the wooden floors in that part of the building.
• Concrete frame structures with beams and columns are present in the corner areas between Body A and Body B, and between Body C and Body D, serving as encasement interventions for the masonry walls. In this case as well, they serve as the supporting element for the composite concrete floors.

A specific campaign of integrated structural and geotechnical investigations was carried out to develop the structural reinforcement project. Material analyses were performed to determine their structural and mechanical characteristics (tests with double flat jacks, compression tests on mortar samples, thermographic surveys, penetrometer tests on wooden beams).

The structural issues of the former convent: Surveys and investigations conducted on the structural elements revealed a particular seismic vulnerability of the buildings, considering the seismic zone 1 in which they are located. They highlighted several characteristic aspects, some of which are particularly evident:

• The presence of a high irregularity in the architectural layout of the complex, due to the complex plan arrangement of the various buildings and the different stiffness and strength characteristics of the various structural types present in the structures.
• The distribution of masses in plan and particularly in elevation shows a high degree of irregularity, mainly due to the misalignment of the floor levels in the various buildings.
• The lack of closure of the masonry boxes, resulting in the absence of a confinement effect under the shear forces induced by seismic action.
• Insufficient stiffness both in-plane and out-of-plane of the horizontal elements, resulting in their limited capacity to transfer horizontal actions to the walls.

A pronounced pattern of cracking characterized the southwest corner (Body B-C) with cracks distributed on the walls at an inclined angle of approximately 45° and significant opening of the cracks, measuring about 5 mm in width. These damages are attributed to settlement phenomena in the foundation.

The investigation activities aimed to assess the current state of the architectural complex demonstrated the inoperability of the existing structure and the need for a repair and structural reinforcement intervention to accommodate the planned new use.

Where and how the intervention was chosen: The ongoing project includes all the necessary interventions to eliminate or significantly reduce the serious deficiencies in the structures, resulting from design and construction errors, degradation, damage, or transformations. It involves reinforcing the existing structure, particularly in relation to the changed structural requirements of the new intended use.

The seismic improvement interventions carried out have led to a significant change in the stiffness, strength, and/or ductility of individual structural elements.

Additional structural reinforcement interventions were carried out by filling the existing wall panels with lime-based mortar and regenerating the internal core with grout injections. New transverse connecting walls (shear walls) were also introduced, concealed within the existing partitions, to improve the overall seismic behavior of the structure and increase its transverse restraint.

Furthermore, to address the identified foundation settlement issues, micropile interventions were carried out along the perimeter of the structure to limit the development of differential settlement phenomena.

The intervention utilized the CRM RI-STRUTTURA system by Fibre Net. The reinforcement of load-bearing walls involved all the building sections of the architectural complex, covering almost the entire perimeter wall surface and the main internal partitions.

To ensure structural efficiency, the CRM (Composite Reinforced Mortar) technique was applied to both sides of the wall surface in certain areas, considering the entire height of the building and aiming to minimize discontinuity caused by the presence of inter-floor slabs.

The Fibre Net CRM R-ISTRUTTURA system employed includes the use of a composite material network made of Glass Fiber Reinforced Polymer (GFRP), GFRP angles, and connectors. These elements are applied to the properly prepared wall surface.

In the case of reinforcement on both sides of the wall, the preformed mesh network with a 66x66mm grid was transversely connected using appropriately sized connectors (15+90cm). This ensures optimal collaboration between the reinforcement and the wall substrate, improving the mechanical characteristics (shear resistance) of the structure.

The GFRP connectors were regularly spaced and installed according to the project specifications for the entire wall surface area involved in the mesh installation, covering approximately 3500 square meters. The reinforcement intervention concluded with the application of a finishing plaster layer based on NHL hydraulic lime.

This intervention ensures high durability even in the presence of chemically aggressive mortars such as lime-based ones, thanks to the use of preformed networks made of AR glass fiber and thermosetting resins. The extensive application of this system not only improves the peak strength of the masonry but also provides widespread ductility to the structure, while keeping weights and thicknesses limited. The compatibility and high breathability of the proposed CRM system allow its use on historic and protected masonry structures.

Fibre Net Materials and Systems

• For MASONRY CONSOLIDATION with the CRM RI-STRUTTURA system:
  • FBMESH66X66T96AR – GFRP mesh with a 66x66mm grid, approximately 3500 square meters.
  • FBCON L – GFRP connectors with dimensions of 20cm and 15+90cm, section 10x7mm.

Construction Details Location: Vibo Valentia

Contractor: Deodato Francesco, Ionadi (VV) | 2018-2019.