A polymeric measuring beam comprising a core with a shaped stress concentrator with cylindrical delimiting surfaces and measuring systems or elements thereof located in the area of highest stress and uniformly bonded with the material of the beam core; the beam core being made of a thermoplastic polymeric or duroplastic polymeric material: thermosetting or chemically curing, is characterized in that the stress concentrator, in the longitudinal section of the beam, has a shape defined by at least one circle or at least one closed curve, symmetric or asymmetric relative to the vertical or horizontal axis of the local coordinate system of the concentrator, the shape of which is limited by two lines imposing the condition of convergence in the direction opposite to the desired stress increase gradient along the axis of the beam, and such shaped stress concentrator may be arranged symmetrically or asymmetrically relative to vertical or horizontal axis of the beam.