Strut-and-Tie Model (STM), conceived by the French builder François Hennebique as a simple representation of a reinforced concrete element subjected to shear and bending, has been later developed by Ritter and Mörsch.

In the twentieth century several studies have been carried out about STM and the results became the basis of some prescriptions in many international codes.

Schlaich et al. 1987 proposed a global approach to the design of structures using STM.

Even though the use of STM has becoming widespread, several difficulties still exist in deciding which is the model that best fits the actual configuration. This problem is particularly relevant when dealing with non-standard cases.

In this paper, the case of bridge floors subjected to horizontal actions is presented.

Different methods to reach STM are shown: from Load Path Method to FEM to optimisation criteria. The aim is to use the examined case to evaluate the efficacy of these methods to gain experience in designing r.c. structures with STM. Moreover, in the paper the influence on the model of the distribution of the restraints, of both the geometry and the stiffness of bridge floor as well as those of longitudinal and transversal floor beams are investigated.