The paper synthesizes the research work of the Florentine school in the semiautomatic recognition of Strut and-Tie Model in reinforced concrete (R.C.) structures. The first contribution goes back to more than ten years ago and consists in the implementation of a simple iterative method, based on results of linear elastic analyses, where the STM is obtained through the progressive removal of the under stressed regions. A second method, called the “crest lines method”, identifies the truss model with the crest lines of the principal stress fields in the linear elastic field or in the non linear one. The last method, implemented more recently, uses a topology optimization technique to search, through the combination of linear elastic FE analyses and an optimisation algorithm, the material distribution with the maximum stiffness, which corresponds to the strut-and-tie model.