This paper presents the results of a study of pliable flange connections in steel frame. Calculation of the load carrying capacity and ductility of flange connections is an important design stage and requires consideration of various factors such as analysis of mechanical properties of materials, geometry, operating conditions and type of loads. The main objective of structural design is to ensure structural safety while minimizing cost. For this purpose, it is necessary to use calculation schemes that correspond to the real physical operation of structures. In solving this problem, the following were used: full-scale experiments, finite element method and analytical method of limit equilibrium (LEM), which is traditionally used in structural fracture mechanics. The influence of bending stiffness of the flange on the process of joint failure is investigated. A new design solution of a pliable beam-column assembly is proposed, which is characterized by simplicity of calculation and assembly.