PSI - Issue 84

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

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4.1. The Sliding Intrados Deviator: Static and Construction Advantages One of the distinguishing features of the system lies in the elimination of fixed constraints in the lower area of the beam. Unlike traditional post-tensioning techniques (which use strands or Dywidag bars and require rigid anchors or fixed 'saddles' for the transfer of deviation forces), the CAM-Bridge ® system uses a sliding deviator device .

Fig. 4. CAM-Bridge ® System application. Sliding deviator device ensures normal force equalization between diagonal and horizontal branches

The technical solution provided by the system offers two decisive engineering benefits:

• Uniformity of Stress State: Relative sliding between the strip and the deviator ensures normal force equalization between diagonal and the horizontal branches, simulating the efficiency of a continuous parabolic profile. • Preservation of Existing Structures: Shifting anchorage points exclusively to the slab avoids interference with critical zones in the P.R.C. beam's bottom flange, which are typically congested with pre-stressing reinforcement and stirrups. This mitigates the risk of shearing existing armatures during installation.

(a) (b) Fig. 5. (a) Conventional post-tensioning layout with fixed deviators. The post-tensioning effects on the diagonal and horizontal reinforcement branches remain decoupled, preventing stress equalization.; (b) CAM-Bridge ® application layout. Due to the sliding deviator, the system is equivalent to a continuous parabolic profile. System activation induces participation in flexural resistance and significantly reduces shear stresses at supports, simultaneously increasing the flexural stiffness of the reinforced element.

Fig. 6. Experimental setup of the CAM-Bridge ® system applied to a prestressed bridge girder at the DiST laboratories in Naples. The test validated the retrofitting of existing beams with initial prestress loss, which was successfully recovered through the system application.