A method of and means for measuring bending moments, shearing forces and other stresses in a loaded structure

摘要

423,452. Testing physical qualities of materials. IBANEZ, J. A. M. V., 55, General del Canto Street, Santiago, Chile. Oct. 6, 1933, No. 27539. [Class 106 (ii)] Comprises a method for the direct measurement of bending moment, shearing force, &c., in which a scale model of the structure is provided with a gap at the place of measurement and a measuring instrument is fixed to the model on opposite sides of the gap and adjusted to annul the deflection by producing an opposite bending moment &c. Fig. 1 shows diagrammatically the measurement of the bending moment of a member X, Y of a rigid frame. The two frames A, B of the instrument are rigidly connected at 1, 2 to the free ends of the member X, Y where the gap occurs. A flexible plate G is joined to A at 9 and to B at 8. A force P acting at the point a produces a bending moment at the middle point of the flexible plate G. A spring C is rigidly connected to A and B at 3, 4 and is deformed under the action of the bending moment. A spring D connected to the spring C at 5 bears against a screw T. Another spring E is fixed to A at 6 and to B at 4 and is connected to an indicating needle F, the free end of which is observed through a microscope H. Under the influence of the force P this free end moves to the right and is restored by moving the screw T an amount which is a measure of the bending moment. If instead of rigidly connecting the points 1, 2 of the instrument A, B to the free ends of X, Y, the points 10, 11 are connected as shown in Fig. 2, the longitudinal stresses in X, Y will produce a moment equal to their value multiplied by the distance between 10, 2 and 11, 1, the sum of which and the bending moment is measured by the instrument. To measure, shearing force, the instrument is connected to the model at the points 10, 14, Fig. 3, in which an angular arm L is joined to the frame B by an elastic plate J rigidly fixed to B at 2 and to L at 13, the arm L being also joined to a plate K rigidly fixed to an extension of B at 16. The instrument measures the sum of a moment comprising the product of the shearing force at 14 and the distance between 13 and the centre of J plus the bending moment. A constructional form of the instrument A, B is described as are suitable forms of structural members for building the model, such members being made of duralumin plate, wood, celluloid, &c. in standard sizes.