ABSTRACT
This chapter presents some preliminary analyses devoted to the identification of suitable models able to provide the frequency decay of a damaged masonry structure on the basis of the observed damage pattern. The long term monitoring of bridges requires information about the signatures produced in the dynamic properties of the bridge by the deterioration factors acting on the bridge itself. While in general for concrete and steel bridges the most influential factors are localised damages produced by impacts or fatigue cracks, in masonry bridges a very important role is played by environmental degradation of mortar and blocks. The influence of the structural damage in terms of change of natural frequencies is dealt with by introducing in the static equivalence to the dynamic vibration formula, the effect of the damage as a change in the curvature diagram. The importance of defining a sensible and effective damage detection procedure is evident.
