The article deals with the relevance of the stress strain state (SSS) in areas of potential destruction for the assessment of deformed structures strength. The article develops a calculation and experimental method for building a combined strength criterion equation involving strength coefficients, introduced by Pisarenko-Lebedev criterion equation with regard to the real SSS type. The proposed method has been implementedand experimental mechanical tests were carried out for the selected samples which follow the idea that the SSS type in the active zone is identical to the SSS of the analyzed structure in the area of interest. Results of the calculations and experimental tests demonstrate a significant decrease in the limit strength value for 50CrV (high quality) under biaxial tension in comparison with the conventional limit strength value.