Calculation of metal elements deflection using a three-line strain diagram

In the article, using a three-line symmetrical strain diagrams for metal, a technique is given for constructing a «moment-curvature» diagram, which is important for determining the deflections of steel beams. Approximations of the moment-curvature diagram by polynomials of the third and fifth degrees, which have high accuracy, are proposed. In numerical examples, it was established that when plastic deformations develop, it is not permissible to determine deflections using a linear model. In addition, numerical examples show that physical nonlinearity has little effect on internal forces in statically indeterminate systems, but has a strong effect on the stress-strain state.