Study on the mechanical behavior of ballastless track continuous welded rail on multi-span simply supported steel truss bridge for mixed passenger and freight railway

Ballastless track continuous welded rails (CWR) are used on a multi-span 100 m simply supported steel truss bridge of a mixed passenger and freight railway, to study the mechanical characteristics and influence factors of CWR on the 100 m simply supported steel truss bridge, a track-bridge-piers spatial finite element model was established based on the track-bridge interaction (TBI) principle. The influence of design parameters such as the number of bridge spans, the longitudinal stiffness of piers of the simply supported steel truss bridge, the arrangement of bridge bearings, the type of rail, and the track longitudinal resistance type on the mechanical characteristics of CWR on the simply supported steel truss bridge were systematically examined. The research results indicate that for multi-span simply supported steel truss bridges, the model can be simplified by considering 8 spans when the total number of spans exceeds 8. Likewise, when the number of adjacent concrete box girder spans exceeds 5, 5 spans can be adopted. The longitudinal stiffness of piers of the simply supported steel truss bridge has a significant influence on the rail braking force and the rail broken gap. Increasing the longitudinal stiffness of the piers from 399kN/cm to 5000kN/cm has a much greater effect on the forces and deformations of CWR on the bridge than increasing it further from 5000kN/cm to 10000kN/cm. The bridge expansion length is primarily governed by the arrangement of fixed bearings on the adjacent concrete box girder. Therefore, to reduce the forces in the CWR on the bridge, the simply supported steel truss bridges and the adjacent concrete box girders should adopt a consistent bearing arrangement. In addition, rails with a larger cross-sectional area can reduce the additional rail stress. The used of small resistance fastener systems for ballastless track decreases the rail expansion force and rail braking force by 56.72% and 18.05%, respectively, but it increases the rail broken gap by 37.49%. The research results can provide references for the design of CWR on the simply supported steel truss bridge.