We present in this paper a study regarding the effect of mass variation on the vibration response of a beam-like structure. During operation, the structures can be exposed to the action of supplementary masses which additionally load them and change their dynamic behavior. These loads can be therefore observed and assessed from the changes in the natural frequencies since the mass increase leads to a frequency decrease. To find the effect of increasing the mass of a beam slice, we used the law of conservation of mechanical energy. The total stored energy is unaltered from the mass change and equals the total kinetic energy. Hence, increasing a slice's mass has as a consequence the velocity decreases, thus the frequency decreases. We succeed to demonstrate that the slice position in the beam is crucial for the frequency change in each bending mode and found a relation for the calculus of a coefficient that can be used to predict the frequency changes due to a local mass alteration. The relation was successfully tested against experiments.
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