The influence of inaccuracies of laying tracks on the loads acting on bridge cranes

The problem of increasing the life time of running wheels of bridge cranes is a subject of many studies. The life time is determined by the wear of wheel flanges, which depends on the intensity and time of action of lateral forces applied to the crane during its extended motion with a constant velocity of the center of mass. Until now, the lateral forces were considered to appear mainly due to the adverse combinations of mounting angular misalignments of axles of running wheels. This article examines changes in the level of lateral forces due to the track laying inaccuracies. For this purpose, a single-mass dynamic model of a crane is introduced. The model takes into account that the crane can move along and across the crane tracks, as well as to rotate about the center of mass. Under the action of lateral forces, the running wheels can have linear and angular elastic displacements and the wheel axle can have different mounting angles of skew. The differential equations of motion of the crane take into account the driving forces generated by motors, resistance forces, lateral elastic slip forces and the forces generated due to the contact of wheel flanges and rails, which are considered to depend on the stiffness of crane tracks. The elastic slip forces are described by the functions of linear and angular movements of wheels. However, they depend on the mounting angular misalignments of wheel axles. At high speeds, these slip forces are constant and equal to the forces of dry friction. Various forms of crane runway inaccuracies are considered and the lateral forces are determined. The maximum values of lateral forces are about two times higher than the corresponding values obtained for the same mounting misalignments of wheel axles, but for the parallel straight paths. The calculations show that the inaccuracy of stacking crane tracks in the plane is also one of the main factors influencing the level of lateral forces. The research results can be used to revise specifications for the laying and operation of crane tracks.

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