چكيده به لاتين
The loads on railway tracks are dynamic load. The loads transmitted to the track and its components cause vibration. The vibrations have undesirable effects on the track structure, especially the railway bridges. Therefore, control of vibrations is one of the main concerns in railway engineering. Various methods have been proposed for controlling vibrations and have been studied on them. One of the newest method to reduce vibrations on railway track is using under sleeper pad. In this study, a comprehensive study of the effects of USP on the vibration of the bridge deck and the components of the railway track were investigated by field test and numerical modeling.
In this research, a concrete bridge in the northern district of Iranian railway through a series of numerical studies was selected. Under sleeper pads were installed in separate stages on bridge sections and transition areas. Field tests were carried out in the presence and absence of these pads. The tests included measurements of acceleration of rails and sleepers, as well as measurement of deck acceleration and displacement. Dynamic responses of the bridge were studied and evaluated in the presence and absence of USP. In order to carry out numerical studies, a 3D bridge and track model with its actual dimensions was simulated in ABAQUS software. After validating of numerical results with the results of field tests, the performance and dynamic behavior of the bridge examined and sensitivity analysis was performed.
The acceleration of the deck after the installation of the USP in the numerical model at first and second span reduced 17% and 38%, respectively, and 50% and 36% in field tests. The acceleration of the rails increased after the installation of the USP in the first span and decreased in the second span. The increase in the first span in field experiments and numerical studies was 40% and 14%, respectively, and the acceleration reduction on the rails in the second span in both the numerical and field studies was 4%. The rate of acceleration in sleeper in the first and second span was 26% on average in field tests.
In the sensitivity analysis, it was found that at high speeds, the presence of a under sleeper pad in the transition zone caused a 20% reduction in deck acceleration. Soft pads also have the most effect on reducing od deck vibrations, so that the soft pad reduction is 11 percent more than of moderate pad and 18 percent more than of stiff pad. With the change in the axle load passing through, it was found that the acceleration in the presence of USP is the same in different axle loads.
