In this paper effects of fractured sleepers on rail track vibration under moving wheelset have been investigated. Two parallel rails of the track have been modeled as Euler-Bernoulli beams on elastic points as rail pads. Also sleepers have been modeled as visco-elastic Euler-Bernoulli beams. It is assumed that, some sleepers under the rail track have been fractured and modeled by two beams. The wheelset has 5 DOF which are longitudinal, vertical and lateral movements plus roll and axial rotations. To determine normal contact force between wheel and rail, relative position of wheel and rail has been determined at each instant. Using the coordinate of each wheel points in rail coordinate system, the penetration of wheel in rail has been determined. To determine rail-wheel contact forces, Hertzian nonlinear contact theory and Kalker theory have been used. A computer program has been developed that numerically solves the equations of motion of the system for different operating conditions using Runge Kutta Cash-Karp computation method. Using this model the effects of wheelset velocity, wagon weight, number of fractured sleepers and fracture location on rail track vibration have been investigated. پرونده مقاله