Introduction. The Russian Federation has adopted a long-term program for the large-scale construction of highways, which will require the construction of a large number of bridges of small, medium and large spans. International experience shows that it is advisable to build road bridges from prestressed reinforced concrete. Moreover, the most effective ones are the span bridge sections of a box-shaped cross-section that are different from girder structures by better aerodynamics, lower labor costs during construction and more attractive external aesthetics. In the literature on numerical analysis of the stress-strain of monolithic reinforced concrete structures, very little information is provided on calculating span bridge structures taking into account concrete creep. The aim of the study was to develop a technique for finite element modeling of long-term deformation of a box section span using an authorized software package. The data from the computational experiments were verified using the ANSYS Mechanical software package.

Materials and Methods. The finite element method in the form of a displacement method in combination with the theory of linear viscoelasticity is employed as a mathematical tool for modeling prolonged deformation of the investigated reinforced concrete structure. In order to formalize concrete creep, S.V. Aleksandrovsky's elastic creeping body model was used. The computational process of numerical integration of the resulting operator-matrix equation is based on the principle of superimposition of effects and the use of the trapezoid formula. The computational experiments were performed on the Microsoft Visual Studio platform and the Intel Parallel Studio XE compiler with the built-in Intel Visual Fortran Composer XE text editor. In order to visualize the simulation results in the form of pictures of the distribution of displacement and stress fields, the descriptive graphics of the Matlab system are employed.

Research Results. A program has been developed and verified for the finite element calculation of reinforced concrete beam structures in a three-dimensional formulation using a discrete reinforcement scheme, according to which the reinforcing frame is modeled by means of two-node beams, and the concrete array is modeled by means of volumetric multilinear finite elements. It is found that for the considered typical box-shaped bridge sections, the adopted pre-voltage scheme is ineffective as it fails to provide the required bending.

Discussion and Conclusion. The results of the calculations of the box section in a linearly elastic formulation obtained using the developed software package and the ANSYS Mechanical software package are compared. A satisfactory coincidence of displacement and stress values at the investigated points has been identified. The stress-strain state of the box section at the stage of prestressing and subsequent loading is investigated. The conclusion is made on the expediency of scientific support at the design stage of such bridge sections in order to increase their load-bearing capacity.