A simple algorithm is proposed for the automatic insertion of nonlinear spring elements to the finite element models during the solution procedure. Frame structures with localized large deformations are conveniently, efficiently and reliably dealt with by the algorithm.
For thin-walled sections, spring elements are inserted to nodes where the bending moment reaches 40 to 80 percentage of the maximum bending moment of the member. The level at which springs are inserted is controlled carefully according to the amount of rotation when the member attains to the maximum bending moment so that the convergence in subsequent incremental stages may be guaranteed. For solid sections, spring are inserted to nodes where yielding beings.
Several examples are sloved successfully without any consideration of the collapse mechanism of the structure. The results are in good agreement with those available in the literature.
