A pair of balanced couples and paires of balanced forces directed toward the normal or the tangent of the curved beam lying in a plane are defined. On the basis of the principle of virtual forces it is shown that the local deformations are the corresponding generalized displacements. These generalized forces are applied in the Theory of Structures. First, for determination of the derivative (referring to the second argument) of the influence functions for generalized displacements or for cross section resultants of the elastic curved beam due to the unit force in the normal or in the tangential direction. The influence of the axial forces and the shear forces on a beam deformation is taken into account. The mentioned derivatives of the influence functions are used in the second order theory. Second, for determination of a generalized displacement of a curved beam due to a known „concentrated” deformations. This is shown in the example.