چكيده به لاتين
Concrete bridges are one of the most important and sensitive parts of the railway network. These structures are affected by different vibrations during the operation of the track. The presence of local irregularities at the junction of rails is one of the main sources of vibration in the bridge structure. Irregularity created in this area due to 1- in direct contact with wheels of vehicle and 2- short wavelength of roughness, cause significant dynamic shocks in the railway structure. The impacts were created to affect the dynamic behavior of the bridge. In this study, in order to investigate the reaction of concrete bridges to the vibrations generated, an analytical algorithm consisting of moving (train) and fixed subsystems (track and bridge structures) is presented. The mentioned subsystems are modeled using Multi Body Dynamics (MBD) and Finite Elements Method (FEM), respectively, and then connected by nonlinear contact between wheels and rail. One of the most important findings of the present study is a significant increase in the acceleration of the bridge due to vibrations caused by local irregularity, especially in 1/4 of the initial and final areas of the bridge. These conditions increase sharply at speeds above 100 km / h. Besides, by examining the force acting on the deck of the bridge, it was found that this force can increase up to 150% of the axial force of the wheel in the presence of local irregularity. Also, by studying the geometry of local irregularity, it has been shown that unlike long-wavelength irregularity, vibrations will be increased with an increasing wavelength up to the range of 450-550 mm.
