چكيده به لاتين
“Under Ballast Mat” (UBM) refers to integrated elastic layers made of industrial and cellular polyurethane foam or resilient and elastic recyclable granular rubber, and their most important characteristics are their static and dynamic modulus. These layers have recently become widely used in the world rail industry to protect ballast and its corrosion by increasing contact area and distributing loads more efficiently, utilizing in “Transition Zones” to reduce non-uniform settlements and load impacts, as well as reduce transmitted noise and vibrations from railway tracks to the surrounding structures. The most important purpose of these mats is to mitigate noise and vibrations in railway tracks.
In this study, in order to control the vibrations (vertical deflections and accelerations of rail system and structure), a concrete bridge at the Tehran Metro Line 5, in 25 + 755 km, near the “Atmosphere” station, was studied. The vibration rate and performance of the bridge structure before and after installation of these high elastic mat was examined. In addition, numerical analysis of the movement of an on-line locomotive on a concrete bridge and the physical and mechanical parameters of the resilient layer, bridge, and rail and fleet components are studied to investigate the effects of these parameters (Such as axial load, speed of locomotive movement, mats type, etc.) on superstructure of railway tracks and bridge structures using programming in MATLAB software. The design UBM is also investigated in order to optimize the maintenance costs of the railway tracks and bridge structures.
The results of this study show that the application of “Under Ballast Mats”, increasing the vertical flexibility of the superstructure and substructure under all conditions. Although increasing vertical superstructure deformations, decreasing vertical bridge deck deformations and decreasing vertical acceleration to the tracks and the bridge structure will be along. In addition, the increase in axial load had the greatest effect on the investigated factors on the values of the vertical deformations of superstructure and deck. And velocity was also the most effective parameter on the values of the track and structural vertical acceleration. As well, changes in speed and compressive strength of bridge deck concrete have no effect on vertical track and bridge deck deformations. Also, changing the type of mats (using harder or softer mats) in the track, reduces the vertical deflections of the superstructure, but increase the vertical acceleration of the bridge deck.
