IMPLICAZIONI DELLA DISTRIBUZIONE DELLA MASSA NELLA MASSA MODALE, CORRELAZIONE DEL MODELLO E RILEVAMENTO DEL DANNO.

Mode shapes can be normalized in many ways, so the modal mass of a mode shape is not unique because it is directly related to the normalization method. The mode shape length depends on the mode shape and on the volume distribution in the structure. The modal mass in constant mas-density systems is equal to the product between the total mass and the mode shapes length squared, so a relationship between the modal masses of the different modes exists: all the modal masses can be estimated from only one mode modal mass known. In non-constant mass-density systems, the apparent mass is different for each mode and depends on the mode shape and the mass distribution in the structure. Further studies on the cross length have been carried out for both the systems. This new concept can be used to know how the mass is distributed in the structure. Numerical simulations have been performed on different structures to study the influence of FEM parameters variation on the Length evaluation. Two lab-scaled structures were tested by OMA to investigate the accuracy of the equations proposed to merge modal masses and cross-length.