Long-term concrete behaviour are two subjects of current interest in many studies published over the last decade. This thesis project is dedicated to the study of both the above mentioned topics, developing a comprehensive work that can further bring a higher degree of knowledge of the subject and the state of the art today. The first part of the work is devoted to the study of creep phenomena on reinforced concrete beams, creating a model that describes the real behavior of the structure, evaluating strains and long-term deformations, which cause phenomena of stress redistribution and delayed breakage over time. In this regard, a numerical model will be presented to evaluate the effect of the phenomena of increased deformations linked to time, such as linear creep, non-linear creep and shrinkage. This model was then applied to a case study, which allowed the evaluation of the degree of reliability of the proposed model. The second part of the work, instead, is dedicated to the study of the phenomenon of ductile breakage of beams subjected to bending. In particular the study concerned the influence of metal fibers on the degree of ductility of the structure. A test campaign was carried out, which made it possible, through an analysis of the results obtained, to assess the effect of the fibres on the breaking of the compressed area of the beams. The laboratory tests on fibre-reinforced concrete beams conducted as part of this study have shown that the presence of metal fibres within the concrete matrix increases the degree of ductility of the structure and also the displacement capacity after breakage.