The main problem considered in this article is prediction of strength for welding structures of hoisting equipment. Developed is a method of estimation of plastic strain limits for welding structures that takes into account all the most important factors influencing strength and plastic properties of a welding joint (such as stress concentration factors and residual stresses, environment temperature). These factors are implemented with the help of a special welded model. The static test, described in this article, was conducted at normal temperature. Analysis of the stress-strain state of the fracture area is based on the finite element method. As a result of investigation the limits of the plasticity of the welding joint were estimated