Computational algorithms with nonreflective boundary conditions for modeling the dynamics of an elastically supported load-bearing structure

The article compares the variants of dynamic models of mobile load to describe the joint oscillations of span structures and vehicles of road bridges, taking into account the irregularities of the road surface. Using the example of a known solution to the problem of oscillation of the beam system when the sprung load moves through a single unevenness, the application of the method of joint modeling of an inert mobile load and a span structure in the LS-Dyna FE complex using contacts is considered. The proposed method eliminates the need to use special plugins to describe the dynamics of the car and allows to consider the calculated situations with the separation of the wheel from the road surface. At the same time, the use of contacts to create dynamic models of vehicles in the FEM is complicated by the lack of a verified way to account for road surface irregularities. In bridge calculations, spatial modeling of an elastic layer of pavement with irregularities leads to the fact that the rigidity of the span structure varies in length depending on the micro profile. An effective way to solve this problem is to use solids with orthotropic properties of the material to describe the geometry of irregularities. Due to the unequal mechanical properties of the material along and across the beam, the layer with irregularities adequately transfers the load from the vehicle model to the supporting structures and does not affect the rigidity of the span structure. A good coincidence of the results of solving the dynamic problem by the proposed method in LS-Dyna with the results obtained by other authors in the SAP2000 program shows the possibility of using contacts for dynamic calculation of bridge structures taking into account the irregularities of the road surface.