The article deals with the issues of simulation of the dynamic moving load on a span structure in the modern finite element systems. The possibility of using the contact conditions in the Midas NFX program to describe the coupled vibrations of a beam and a movable load is investigated. To verify the results obtained, the method of separate modeling of the moving load by use of several forces on the trafficway line is used. The series of numerical studies of an elastically supported dynamical system was performed using two techniques. Graphic charts are obtained mapping vertical displacements of the vibration system characteristic points, depending on the inertial properties of the moving load, on the nodal forces application step, the parameters of surface conditions.

To simulate the non-linear vibrations of a floating bridge of a continuous system on separate floating supports with additional limiting supports at the ends with a moving load solves the most complicated problem which is the problem of describing the behavior of a span structure. A technique for simulating the vibration of an elastically supported deformable rod with limiting supports at the ends, which is a design scheme of a span structure, under the action of a moving force is developed. A computational algorithm for solving partial differential equations with varying boundary conditions is proposed, which includes boundary conditions in the model equations and does not require the subordination of basis functions to the boundary conditions. During the calculation, the basis remains constant. Piecewise linear basis functions are used to solve the differential equation. The technique is tested using a computational program Matlab, which is implemented when performing numerical studies of the behavior of the dynamic system as a function of the parameter changes. The developed technique is universal for studying the dynamics of a number of constructively non-linear systems.