investigating on the effects of random irregularities of railway track by half-bogie model

the vibrations produced by trains include two parts which are deterministic and random vibrations. due to variation of dynamic loads and patterns of load-time, the random vibration of moving train is one of the most important issues in the field of railway engineering. one of the important sources in producing the train vibrations is rail roughness and irregularities. in this paper, responses of vehicle and railway components caused by half - bogie have been investigated. the model of moving vehicle on the railway track is considered as a half-bogie with two degrees of freedom. the connection elements between wheel and bogie are spring and damper. also, model of railway system is considered as a beam on a rough surface. after modeling, equations of motion have been extracted for half-bogie and rail system. then, motion equations of deterministic vibrations have been validated. the results indicated that the responses had good agreement with responses of previous studies. after validating, random equations have been presented in two domains that are time and frequency domains. for analyzing the random vibrations, track irregularity is applied as random, and power spectral densities are selected based on fra organization. analyses are performed based on half-bogie and railway parameters. the results have been presented for beam, sprung and un-sprung masses. also, the results show that the maximum power spectral density of beam decreases with the increase of speed parameter.