This paper deals with shear force and bending moment identification in a beam from measured displacement. The proposed approach, using the weak form of the equation of motion, is based on the extraction of shear force or bending moment from integral equation and choice of test functions, associated to each boundary quantity of interest. After the theorical description, numerical simulation results are shown in order to clarify limits of the method and to stress its self-regularization. Two experimentations are described, showing very good accuracy of shear force and bending moment reconstruction in comparison with direct measurements.