The article assesses stiffness of main trusses bolted connections in the railway bridges metal superstructures. The generally accepted approach for trusses of bridge structures analysis is to replace joints with hinges. This technique simplifies finding the forces in structure elements, but reduces the reliability of the design model. In this study, the finite element method implemented in the Ansys Mechanical software package is used. The process of determining the stiffness of the high-strength bolts joint connection is described in detail. The paper proposes formulas to determine rotation angles of the truss elements joint sections according to the finite element model analysis results. For two joints of a standard design, superstructure stiffness was determined: kN2 = 107183.06 kN×m/rad, kN3 = 137605.56 kN×m/rad. Graphs of bending moment on the rotation angle dependence were also made. It was concluded that the beam model of the structure shows underestimated values of the joints stiffness, and the difference with the stiffness determined for the detailed finite element model can reach 5.635.