This study investigates the rail-structure interaction (RSI) phenomena for implementing continuous welded rail (CWR) on an unballasted simply supported steel through girder bridge with a span of 78.8 m designed for Dedicated Freight Corridor (DFC) loading (32.5t axle load). A comprehensive parametric analysis was conducted using MIDAS finite element modeling and theoretical calculations based on UIC774-3(R) guidelines to evaluate axial stresses in rails and relative displacements between rail and deck under braking/traction forces, thermal variations, and vertical train loads. The results demonstrate that braking loads (16.3 kN/m) generate moderate stresses (20.3 and -26.6 N/mm²) at both fixed and free supports, while temperature effects (35°C) induce significantly higher stresses at the free support (-76.3 N/mm²) compared to the fixed support (2.7 N/mm²). Vertical bending effects produce the most critical stress condition, with compressive stresses at the free support (-80.4 N/mm²) exceeding the allowable limit of 72 N/mm². Although horizontal displacements (1.68 mm) remain well below the permissible limit of 5 mm, the combined stress state necessitates the installation of Switch Expansion Joints (SEJ) at support locations to ensure track stability and structural integrity. This research provides practical guidelines for determining appropriate rail configurations on steel through girder bridges and demonstrates a validated methodology for RSI assessment applicable to heavy-haul railway infrastructure design.
