PSI - Issue 44

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Marianna Leonori et al. / Procedia Structural Integrity 44 (2023) 1022–1029 Author name / Structural Integrity Procedia 00 (2022) 000–000

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2.3. SOL-CAM ® system for joist and hollow block slabs SOL-CAM ® patented technology uses features of the CAM ® System, but is applied to joist and hollow block slabs. It guarantees simultaneous shear and bending reinforcement, Leonori and Vari (2019). In more detail, SOL-CAM ® provides the positioning of two steel plates at the intrados extremity of the joist. The plates are connected by a double bundle of pre-stressed metal strips that are bending reinforcement. Each plate is kept in place to the joist not through bonding, but through ribbons which are arranged to bracket the joist with inclination preferably at 45° from the vertical plane or at any rate in a range between 30° and 60°. The application of the inclined belt is possible without the demolition of the hollow flooring block, using only drilling. The ribbons wrapping the joists are shear reinforcements, but also act as ductile connectors for the lower plate.

Fig. 6. SOL CAM® arrangement

This system is definitely advantageous compared with other systems available for slabs strengthening. The main problem is that usually reinforcement should be bonded onto non-degraded concrete which is rare for existing slabs. SOL-CAM ® is a unique dry application system based on mechanical anchorage. Moreover, it’s the only way to make a shear reinforcement without demolition because a joist is a member not requiring shear reinforcement that then becomes shear reinforced with obvious advantages in resistance and ductility. Ribbons reinforcement allows a shear resistance beyond the cracking of concrete, which is the reason for the brittle collapse of the non-reinforced joists. There is no need for shoring works because SOL-CAM ® allows the improvement of the floor at the time of application. In fact, due to pre-stressed ribbons, it actually de-stresses the joists. Thanks to a recent research project, carried out by Edil CAM Sistemi Srl and the Federico II University of Naples, it has been possible to numerically test SOL-CAM ® on joist and hollow block slabs specimens. Three reinforcement configurations were tested: 1D reinforcement specimen has 1 diagonal bracket each of 3 overlapping strips and 1+1 horizontal ribbons; 3D reinforcement specimen has 3 diagonal brackets each of 3 overlapping strips and 3+3 horizontal ribbons; 5D reinforcement specimen has 5 diagonal brackets each of 3 overlapping strips and 5+5 horizontal ribbons. As anticipated, the diagonal ribbons work both as an anchoring system of horizontal ribbons and as shear reinforcement for the joist. The optimal configuration is one in which the overall strength developed by the horizontal

ribbons is equal to the horizontal component of the diagonal ribbons. The main results obtained can be summarized in the following points:  Horizontal ribbons work integrally as additional bending reinforcement.  The diagonal strips work integrally as bent-up bars without any reduction.

 The pre-stress state, which is a standard feature of the CAM ® System, produces a further shear-bending de stressing effect on the joist that is immediately improved (relative negative deflection is measured) and allows the application in the absence of preparatory devices (supports).  The lower plates can slide or be bonded without affecting the result.