BETONTEX – Functional adaptation works at College Don Nicola Mazza – Verona

An intervention to strengthen reinforced concrete pillars using carbon fiber wrapping technique in the context of a 20th-century architectural setting that underwent extensive renovation in the 1960s. The ‘Don Nicola Mazza’ University College is a cluster of buildings, each serving various activities related to university education.

The architectural complex on Via San Carlo in the center of Verona is the historical seat of the Don Mazza Institution and serves as a male college. The structural adaptation interventions affected two adjacent buildings, connected to each other, constructed in different eras.

BUILDING 1 – Built in the 1960s, it consists of a basement, ground floor, first, and second floors. It features reinforced concrete walls in the basement and reinforced concrete frames with reinforced concrete and brick floors in elevation.

BUILDING 2 – A historical building constructed before the 1900s, it underwent extensive renovation in the 1960s, which preserved only the facades while completely reconstructing the interior with reinforced concrete frames and reinforced concrete and brick floors. It has a ground floor, first and second floors, and no basement.

STRUCTURAL ANALYSIS

In the absence of documentation regarding the existing structures, the analysis of the buildings was initially conducted visually and then through calculations. The buildings did not exhibit significant cracking patterns, although some vertical cracks near the joint between them were attributed to thermal movements. The structural analysis utilized all available information obtained through inspections, surveys, realistic reconstruction of construction techniques, and technical knowledge from the era of construction. Additionally, investigations were carried out to determine the geometry of structural elements, and material tests were conducted to determine their characteristics. Subsequently, the structural analysis and verifications were performed using computerized calculation software (Domen Win).

INTERVENTION

The project did not involve a change in the intended use but focused on functional adaptation. The seismic improvement works were accompanied by the construction of an external reinforced concrete staircase (in the courtyard) and an elevator block in the historical building. Regarding seismic aspects, the planned works were based on the results of assessments of the current state and evaluations of the structure’s safety level under seismic conditions. According to these assessments, it was necessary to reinforce many pillars with flexural reinforcement and some pillars with shear reinforcement. Adequate measures were also taken to address the risk of impact between the two buildings. Regarding the foundations, no distress was observed, and they were deemed suitable for the loads they had been subjected to throughout their history.

REINFORCEMENT OF PILLARS WITH CARBON FIBER

The reinforcement intervention on the pillars using carbon fiber wrapping was carried out after several preliminary operations to prepare the surface of the pillars for proper material application and subsequent vertical and horizontal wrapping according to the project specifications.

PRELIMINARY OPERATIONS

• Manual or mechanical removal of existing plaster and deteriorated concrete portions at risk of detachment.
• Possible passivation of steel reinforcements by applying cementitious mortar with a brush.
• Possible reconstruction and regularization of reinforced concrete with compensated shrinkage one-component cementitious mortar.
• Rounding off all sharp edges to achieve a suitable curvature radius.
• Vacuuming all surfaces involved in the intervention to remove heavy dust.

REINFORCEMENT WORKS: INSTALLATION OF FIBER WRAPS

• Creation of f14 through-holes in the wall slabs and removal of dust using compressed air.
• Cutting the FRP fiber bundles into appropriate lengths and immersion of one end in epoxy resin, insertion into the slabs, sand filling, and drying.
• Installation of the remaining portion of the fiber bundles, freed from the mesh, properly frayed, impregnated with epoxy resin, and spread radially on the pillar.

PRELIMINARY OPERATIONS

• Manual or mechanical removal of existing plaster and deteriorated and detached concrete parts.
• Possible passivation of metal reinforcement by applying cementitious mortar with a brush.
• Possible reconstruction and regularization of reinforced concrete structures using a one-component cementitious mortar with compensated shrinkage.
• Rounding off all sharp edges to achieve a suitable radius of curvature.
• Vacuuming all surfaces to remove heavy dust.

REINFORCEMENT WORK > INSTALLATION OF PATCHES

• Creation of 14 mm diameter through-holes in the wall slab and removal of dust with compressed air.
• Cutting FRP (Fiber-Reinforced Polymer) patches into appropriately sized pieces and immersion of one end in epoxy resin, insertion into the slab, sanding, and drying.
• Installation of the remaining portion of the patches, released from the backing, suitably frayed, impregnated with epoxy resin, and spread evenly on the pillar.

VERTICAL STRIPS

• Perimeter protection of surfaces by applying a two-component epoxy resin with a roller or brush.
• Smoothing and leveling of previously protected surfaces with epoxy putty.
• Application of vertical reinforcement by installing carbon fiber fabric properly impregnated with specific fluid epoxy resin.

HORIZONTAL STRIPS

• Vacuuming of all surfaces to remove present dust.
• Perimeter protection of surfaces by applying a two-component epoxy resin with a roller or brush.
• Smoothing and leveling of previously protected surfaces with epoxy putty.
• Cutting fabric strips to size to wrap around the entire perimeter of the pillar with at least a 20 cm horizontal overlap.
• Application of horizontal reinforcement by installing carbon fiber fabric properly impregnated with specific fluid epoxy resin.
• Application of dry quartz sand onto the fresh resin to achieve adequate adhesion for the subsequent finishing layer.

After the wrapping operations, the pillars were plastered to protect the reinforcement work and provide them with adequate fire protection coating.

CONSTRUCTION RECORD

PROJECT_Functional adaptation works according to Law 338/2000, D.M. 26/2011, D.M. 27/2011 (buildings D-E)

LOCATION_Verona CLIENT_Istituto Don Nicola Mazza DESIGNER_Ing. E. Magagna,

SINTECO ENGINEERING CONSULTING, Verona IMPLEMENTATION_2014