Experimental Study on Track‐Bridge Interactions for Direct Fixation Track on Long‐Span Railway Bridge

Abstract

e rail and track girder of the direct fixation track (DFT) system on the Yeongjong Grand Bridge (YGB) in Korea exhibit integrated behavior. erefore, unlike the DFTsystem in general concrete tracks, the track support stiffness (TSS) of the DFTsystem on the YGB cannot be evaluated with only the displacement of the rail. e actual TSS of the DFT system supported by the flexible track girders was lower than that of the DFTsystem supported by the general substructure. For this reason, field measurements and a finite element analysis that reflects the actual operating speed of railroad vehicles on the YGB (i.e., Airport Railroad Express (AREX), nonstop Airport Railroad Express (AREX Express), and Korea Train Express (KTX)) were conducted in this study to determine the interactions between the rail and the track girder. e results indicated that the DFT system on the YGB is supported by track girders that exhibit relatively flexible behavior. As a result, the TSS is directly influenced by the bending stiffness of the track girder.

Rail Pad Corrosion Effects on the Dynamic Behavior of Direct Fixation Track Systems in Marine Environments

“…This direct fixation track exhibits integrated behavior because the rail and track girder are rigidly connected together by the direct fixation rail fastening system. Moreover, the direct fixation track system of the Yeongjong Grand Bridge is attached to a long-span special bridge (cable and truss); this concept originated from the track style of the Great Seto Bridge in Japan [2,3]. It is the only such track type in South Korea, and currently condition assessments and maintenance of this track are challenging [2,3].…”

“…Moreover, the direct fixation track system of the Yeongjong Grand Bridge is attached to a long-span special bridge (cable and truss); this concept originated from the track style of the Great Seto Bridge in Japan [2,3]. It is the only such track type in South Korea, and currently condition assessments and maintenance of this track are challenging [2,3]. Other general types of direct fixation tracks have been widely deployed in recent years, and maintenance instructions will be required in the future.…”

“…The stainless steel member attached to the rail pads was corroded in marine condition as shown in Figure 2, and its appearance is concerned about whether the rail pads function properly. In general, the track support stiffness of a direct fixation applied to concrete tracks can be calculated based on the deflection of the rail [2]. The track support stiffness of a specified track structure using soft elastic pads can be directly affected by variations in the spring stiffness of the elastic pads.…”

“…Variations in the spring stiffness of the elastic pads can also cause changes in the vehicle-track interaction force and the dynamic behavior of the entire track system [4]. Therefore, in the case of typical concrete tracks, periodic and timely replacement of the rail pads is important for track maintenance [2,4,10]. Lee [11] experimentally assessed the effect of fatigue on the resilience pads of sleeper floating tracks in South Korea based on the prediction and assessment of changes in their spring stiffness.…”

“…They found that an increase in preload increased the dynamic spring stiffness of rail pads, and thus decreased the track displacement. Another study showed that direct fixation tracks on railway bridges can induce the integral behavior of the rail and the track girder (i.e., the rail support structure as a substructure) by using a harder rail pad, and that the elastic displacement of the rail of the direct fixation track is determined by the bending behavior of the track girder, which acts as a simple beam [2]. Currently, there is no clear standard for the maintenance of rail pads used in direct fixation tracks, and no studies have been conducted on their behavioral characteristics.…”