PSI - Issue 84

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

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Fig. 1: Mean maximum restrained displacements in load bearing (on the left) and shear keys (on the right).

Regarding the results of the reference model (with prestress and 2% damping), all unidirectional bearings exceeded the elastic threshold dy (thus, reached the nominal resistance reported in the design documentation), while half of the fixed bearings remained in the elastic range (PI03 and PI06) and the other half (PI02 and PI07) exceeded the elastic threshold but with plastic deformations much smaller than unidirectional bearings. Comparing the reference model with the other results, different effects can be noted. In load bearings on PI01, PI04 and PI08, neglecting the prestressing action have little to none influence on the results, while on the other unidirectional bearing (PI05) and all fixed bearings the effects related to neglecting the prestress action in the piers are large, from at least 17% up to 62%. Assuming a 5% damping instead of a 2% damping is more influent on the restrained displacements of unidirectional bearing, decreasing the maximum values about 30% on PI01 and PI08 and about 50% on PI04 and PI05. The influence of the damping ratio is relevant also for fixed bearings, but with more effects due to neglecting the prestressing action, with the “No Prestressing (2%)” case showing very close results to the “No Prestressing (5%)” case. Regarding the results about the restrained displacements of shear keys, the most stressed element is the shear key in the bottom slab, which restrains the differential transverse displacements of the two parts on the deck, which is the only one that exceeded the elastic threshold. Neglecting the prestress action in the piers reduces the max displacements up to 12%, but greater effects are reported for considering a higher damping ratio. In fact, in both models with a 5% damping ratio all the shear keys remained in the elastic range. Overall, mean maximum restrained displacements in unidirectional bearings and shear keys are more affected by the damping ratio assumed, while the prestressing action in piers has more influence on fixed bearings. 4.2. Load bearings free displacements Longitudinal displacements of unidirectional and multidirectional bearings, transversal displacements of multidirectional bearings were evaluated and compared to the nominal displacement capacity specified in the design documentation of the bridge. All these results are reported in Fig. 2.