PSI - Issue 84

Alessandro Vari et al. / Procedia Structural Integrity 84 (2026) 975–982

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3.3. Technological Limitations of Traditional Prestressing Despite its theoretical effectiveness, implementing external prestressing with traditional techniques (harmonic steel strands or bars) presents severe operational challenges. Standard practice involves protection via sheaths and mortar grout injections ( grouted tendons ), introducing two insurmountable issues: • Diagnostic Opacity: Mortar sheaths inhibit direct visual and instrumental inspection, making the monitoring of corrosive phenomena (including Stress Corrosion Cracking ) impossible until failure signs appear. • Irreversibility of Tension State: The system becomes static once bonded via injection. Subsequent intervention to compensate for physiological tension losses (rheological phenomena such as relaxation and creep) is impossible, preventing recalibration or re-stressing and rendering the reinforcement incapable of adapting to the structure's temporal evolution. 4. The CAM-Bridge ® Post-Tensioning System Edil CAM Sistemi has developed and experimentally validated CAM-Bridge ® , an innovative external prestressing technology for the retrofitting of existing bridges. Configured as an active "structural exoskeleton," the system cooperates with deck beams through a sliding kinematic coupling. This configuration relieves stress in existing elements and allows for the modulation of the prestressing state based on the structure's deformative response.

Fig. 3. CAM-Bridge ® System application layout. (1) horizontal sections at the beam intrados, prestressed. (2) two horizontally sliding mechanical deviators; (3) diagonal branches anchored to the slab (extrados) The architecture employs stainless steel strips installed with calibrated pretension, replicating the bending moment diagrams typical of gravitational loads in "negative". The standard application scheme includes: 1. horizontal prestressing steel strips at the beam intrados, 2. two horizontally sliding mechanical deviators, 3. multiple order of diagonal branches (steel strips) anchored to the slab (extrados).