الفهرس 
AbstractOnly 14 pages are availabe for public view
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Abstract
The railway sector has witnessed great development over the recent years in Egypt and many other countries. This improvement has been associated with a huge increase in speeds on the lines. High-speeds may cause vibration problems in railway bridges, especially if these velocities lead to resonance phenomenon as the period of these vibrations is on the brink of the natural period of the system. In this research, two alternatives to control the dynamic behavior of steel railway bridges (SRB) are proposed. The first is increasing the superstructure damping by adding fluid viscous dampers (FVD) to absorb apportion of the tremors and reduce the bridge’s dynamic response. While the second is limiting vibration transfer to the bridges by installing laminated rubber bearings (LRB) between deck and piers, those isolators have a lateral stiffness much lower than the lateral stiffness of the structure and can shift the period of the system away from that of the loads. To achieve the purpose of the search, two existing Egyptian steel railway bridges (SRB), one of them is a plate girder bridge and the other is a truss bridge were relied upon to conduct the study. Finite element models were established considering the increase in speeds on structures in their current conditions. After that, they were amended by controlling displacements and/or changing frequencies according to the needs of each case in order to keep pace with the modernizations in the network. The main objectives of the study are to evaluate the effect of those two different alternatives on the response of the bridges and to present practical methods to get the appropriate properties and distributions of these systems in different cases of loading. At the end of the research, the controlling effect of the retrofitting systems, the economic benefits, and the applicability are proven for a vast range of speeds and loads.