The　flexibility　of　the　foundation　system　significantly　affects　the　seismic　and　operational　performance　of　integral　abutment　bridges　(IAB).　The　so-called　pile　isolation　system　can　lead　to　higher　flexibility　in　pile　foundations.　It　consists　in　backfilling　the　pile　hole　with　high-damping　materials　up　to　a　certain　depth　from　the　surface　level.　However,　the　impact　of　this　solution　in　increasing　the　lateral　flexibility　and　reducing　the　seismic　demand　strongly　depends　on　the　scale　factor　and　pile　diameter.　Most　investigations　on　this　topic　are　based　on　experimental　tests　on　scaled　pile　specimens.　This　paper　explores　the　pile　isolation　system＇s　effectiveness　by　conducting　a　multivariate　sensitivity　analysis　of　the　seismic　demand　of　an　IAB　structural　archetype.　The　IAB　archetype　is　modelled　as　a　Winkler　beam　with　a　piece-wise　definition　of　the　subgrade　stiffness　and　equivalent　viscous　damping,　simulating　the　responses　of　the　soil　and　high-damping　particles.　The　simulated　data　are　then　used　to　calibrate　a　probabilistic　formulation　of　the　seismic　demand　reduction　due　to　the　pre-hole.　The　formulation,　calibrated　following　a　Bayesian　approach,　is　used　to　derive　estimates　of　the　q-factor　associated　with　the　damping　pre-hole　for　possible　use　in　engineering　practice.　The　analyses　demonstrate　that　pile　isolation　with　high-damping　material　can　be　effective　but　possesses　a　limited　dissipating　capacity,　with　a　seismic　reduction　factor　of　approximately　1　and　2.