This study investigates maximum vertical acceleration patterns in highly skewed, multi-span railway bridges, focusing on Serviceability Limit State (SLS) performance under increasing operational speeds. A 3D finite element model of a representative Spanish high-speed girder bridge is employed, explicitly incorporating the ballasted track and weak coupling between spans. The dynamic response is assessed using three train excitation models of increasing complexity: the simple moving load model (TLM), a vehicle-bridge interaction (VBI) model, and the latter incorporating track irregularities (VBI- \(\eta\) ). The influence of deck skewness, modal participation, and ballast degradation at the simply-supported span interfaces is examined, along with a comparison to simplified analyses following code provisions. Quantitative results demonstrate that increasing deck skewness, from 90 \(^{\circ }\) to 134 \(^{\circ }\) , significantly reduces vertical accelerations by raising the first longitudinal bending and the first torsion frequencies, thus shifting prominent resonances outside the speed range of interest. While vehicle-bridge interaction (VBI) generally reduces accelerations at high speeds, track irregularities (VBI- \(\eta\) ) can notably influence the maximum response depending on the speed window. The weak coupling between simply-supported spans affects spatial acceleration distribution, with maximum responses increasing near the supports. Additionally, localized ballast degradation at span interfaces impacts local peak accelerations. Comparisons show that code-based simplified models consistently overestimate accelerations above 300 km/h. These findings provide critical data for SLS compliance and speed upgrade assessments in multi-span skewed bridges.
