For the assessment of masonry bridges a crucial aspect the identification of the actual load
bearing structure. To identify and quantify the contribution of all the elements of a bridge, static and dynamic
tests on 1:3 prototypes have been performed; similarity to the real bridges has been retained by reducing not
only the geometric scale but also the material properties. The models have been tested in different settings:
bare arch, arch+fill, arch+spandrel; dynamic tests have been carried out at different levels of load-induced
damage. In this way, it has been demonstrated that all the elements contribute to the load bearing structure and
their contribution grossly estimated. Damages may be recognized only if their extent is large enough to be
detected also visually, so that dynamic tests are useful to discover some hidden element, such as internal
spandrels, rather than for estimating the structural damage. Some issue for retrofitting of these bridges is
discussed on the basis of the experimental results obtained