“…A steel-concrete composite beam is obtained by connecting two beams, a metallic one and a reinforced concrete beam, by means of small metallic elements (connectors) which are welded on the top flange of the metallic beam and immersed in the concrete, in order to hinder sliding on the concrete-steel interface, see see [5]. Under the assumption that the system is at rest at t = 0, that is | x=L = 0, u 1 | x=0 = u 1 (t), u 2 | x=0 = u 2 (t), v 1 | x=0 = v 1 (t), v 2 | x=0 = v 2 (t), ∂v 1 ∂x | x=0 = ϕ 1 (t), ∂v 2 ∂x | x=0 = ϕ 2 (t).…”