In this paper some recent results of an experimental-analytical investigation on the small vibrations of steel-concrete composite beams with damaged connection are presented. Damage was induced by removing concrete around some elements connecting the steel beam and the reinforced concrete slab and consequently causing a lack of structural solidarity between the two beams. Experimental observations suggested the formulation of a one-dimensional model of composite beam, where the strain energy of the connection also includes an energy term associated to the occurrence of relative transversal displacements between the r.c. slab and the steel beam. A comparison with experimental results shows that the proposed model accurately predicts the dynamic behavior both under undamaged and damaged conditions. A damage detection technique based on the measurement of variation in the first flexural frequencies was then applied to the suggested model and gave positive results.
