Strut and tie models and stress fields are methods that can be used for the dimensioning and detailing of reinforced and prestressed concrete structures as well as for the check of existing ones. This paper presents an innovative approach towards the automatic development of stress fields based on a nonlinear finite element analysis. Strut and tie models can also be easily developed from the resulting stress fields. Most of the difficulties of the existing methods for developing stress fields and strut and tie models based on elastic uncracked analyses are overcome. Its application to the dimensioning of structural members in practical cases is detailed and several comparisons with experimental results are discussed.