PSI - Issue 84

Stefano Bozza et al. / Procedia Structural Integrity 84 (2026) 686–693

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Fig. 3: Mean maximum deck joint closure (on the left) and mean maximum longitudinal displacement in shear keys (on the right).

Regarding the results of the reference model (with prestress and 2% damping), both joint closure and shear keys longitudinal displacement are smaller than their displacement capacity, so pounding between elements is not an issue for the case study bridge. Comparing the results of the reference model with those of other cases, observations similar to those made for load bearings free displacements can be made. In particular, the displacements reported for the “NO Prestress (2%)” case show little differences to the reference model, with displacement reductions not larger than 8%. The “Prestress (5%)” case and the “NO Prestress (5%)” case also show very close results, but with maximum displacements from 12% to 46% smaller than those of the reference model. More in detail, displacements reduction due to higher damping are about 19-22% for joint closure, 12-27% for shear keys positive displacements (joint opening) and 28-46% for shear keys negative displacements (joint closure). 4. Conclusion The influence of prestress action in piers on the seismic behaviour of an in-service curved PC box girder bridge with prestressed concrete piers was preliminary evaluated, focusing on load bearings, shear keys and deck joints. A FE model of the bridge was developed, with frame elements for piers and the box girder, nonlinear fiber-based hinges at the base of each pier, nonlinear link elements for load bearings and shear keys, and gap link element at deck joints. Several nonlinear time-history analyses were performed on different models, with and without the prestressing action in the piers and considering different values of viscous damping. Mean maximum displacements in both restrained and free degrees of freedom were calculated for bearings, shear keys and deck joints, and results for the different cases considered were compared. Neglecting the prestress action in the piers shown little influence on free displacements in load bearings, shear keys and deck joints, with differences to the reference case about 5%. Instead, prestress action in piers was more relevant for restrained displacements, with differences to the reference model up to 60% for the maximum restrained displacement in fixed bearings. The damping ratio assumed was the most relevant parameter for unidirectional load bearings and shear keys restrained displacements, as well for all free displacements in deck joints, shear keys and load bearings. Assuming a higher damping ratio (from 2% to 5%) results in displacement reduction up to 52% compared to the reference model, and even higher reduction (up to 66%) if the prestress action in the piers was neglected.