PSI - Issue 44

Giorgio Giacomin et al. / Procedia Structural Integrity 44 (2023) 610–617 Giorgio Giacomin et al. / StructuralIntegrity Procedia 00 (2022) 000–000

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• restoration of the connection between perimeter and spine walls by inserting pultruded CFK bars with improved adhesion in carbon fiber in order to improve the box-like behavior of the building; • reinforcement of masonry by applying, on the external face of the wall faces, FRCM low thickness reinforced plaster consisting of primed basalt fiber nets, a natural hydraulic lime-based mortar and fiberglass anchoring connectors; • surface hooping of the external perimeter walls at floor level of the first and second deck using SRG System technology made with UHTSS galvanized steel fiber fabrics, applied with hydraulic lime-based structural mortars; • reinforcement of a masonry pillar with FRP System technology realised with unidirectional carbon fibre fabrics impregnated in situ with epoxy resin; • reinforcement of some internal masonry with FRP System technology realised with unidirectional and bidirectional carbon fibre fabrics impregnated in situ with epoxy resin. The following paragraphs illustrate the technical specifications and application diagrams of these reinforcement measures. 6. Massive injection of natural hydraulic lime mortars Reinforcement by injection consists of injecting material into stone masonry walls with the aim of filling the voids present inside them. In fact, these walls are often filled with recycled materials which over time, both due to sedimentation and poor quality of the filling, are rich in cavities and not adequate for the structural task required of them. The absence of consistency of the internal part of the masonry is in fact associated with low values of resistance and stiffness of the masonry. The purpose of the injection is to restore the internal continuity of the cracked or disconnected material, allowing to reinforce the wall and to improve its behavior in the plane. This type of technique is defined as 'passive' because it does not require any operations that alter the balance or external appearance of the structure. In particular, the implementation phases involve: 1. pre-injection of water throughout the wall volume to be treated for washing it; 2. sealing the cracks in the masonry and other possible points of leakage of the mixture with LIMECRETE hydraulic lime mortar, after cleaning and washing, and subsequent rendering of the masonry with LIMECRETE or bastard mortar; 3. fixing and sealing the injection ducts with a diameter of ¾ ”h inserted for an adequate depth in the holes previously drilled by means of thrust drilling up to 2/3 of the wall thickness, arranged in quincunxes with a distance between centers not exceeding 50 cm; 4. injection of a binder mixture of the type LIMECRETE IR Class M15 in accordance with Standard UNI EN 998-2, with characteristics of breathability, fluidity and mechanical resistance compatible with the masonry to be injected, carried out at low pressure until the mixture escapes from the ducts immediately above; 5. removal from the wall and its washing, if necessary. 7. Insertion of carbon bars for connecting perimeter and spine walls Subsequently, we moved on to the construction and consequent restoration of the connection of the disconnected walls, through the installation of CFK pultruded carbon fiber bars with a diameter of 10 mm in order to improve the box-like behavior of the building. The application steps are as follows: 1. drilling holes in the masonry with a diameter of 14-16 mm and a length equal to that of the sewing bar; 2. removal of the incoherent material present inside the holes; 3. anchoring, with two-component epoxy adhesive RESIN 75 CE marked, of the CFK carbon bars with a diameter of 10 mm arranged in quincunx with a pitch of 50 cm, inclined and inserted to a depth of approximately 100 cm;