This paper deals with a new method to estimate axial load in tie-rods by means of indirect measurements. The knowledge of this information is of great importance to assess the health of the tie-rod itself and of the whole structure, which the beam is inserted in. The method is based on dynamic measurements and require the experimental estimation of the tie-rod eigenfrequencies and mode shapes in a limited number of points. Furthermore, the approach requires to develop a simple finite element model, which is then cross-correlated with the experimental data by means of a model updating procedure. Extensive numerical simulations and experimental tests demonstrated the capability of the new approach to give accurate estimates of the tie-rod axial load as well as to overcome some limitations of the methods currently available in literature.