Damage Assessment of Concrete Tracks According to Displacement Behavior of Underground Structure

Concrete track systems supported by underground structures may undergo forced deformation due to uplift or subsidence; however, track-type-dependent differences in potential damage locations and influence lengths remain insufficiently quantified. This study compared a sleeper floating track (STEDEF), a precast panel track (B2S), and a direct fixation track (System 336) using three-dimensional finite element analysis. Displacement-controlled uplift and subsidence were imposed on the concrete slab, with selected cases additionally subjected to an 80 kN design wheel load. The three track systems were directly compared under a common imposed displacement of 40 mm for both displacement-only and combined displacement–train-load conditions. Potential regions of tensile- and shear-strength exceedance were identified using code-based concrete strength criteria. Impact-hammer modal tests on a STEDEF specimen were used to examine changes in support conditions associated with resilience-pad pre-compression and near-zero sleeper support. STEDEF exhibited the longest one-sided shear-strength exceedance length, while uplift produced longer tensile-strength exceedance lengths than subsidence in STEDEF and System 336. Modal testing showed a lower natural frequency under simulated support loss and a higher frequency under resilience-pad pre-compression. These findings support track-type-specific damage screening and maintenance prioritization.