STRESSES DUE TO CONCENTRATED LOADS IN RESTRAINED BENDING TESTS

The paper describes an analytical method using finite element techniques for evaluating the “pinching” stresses in a beam subjected to opposing concentrated forces acting on upper and lower faces. These conditions arise in restrained modulus of rupture tests on concrete beams when it is required to know the magnitude of these local stress concentrations in relation to the normal “straight line” flexural stress field. The analytical values are compared with results taken from a photo-elastic model with suitably simulated loading conditions. There is excellent correlation between the patterns of principal shear contours as plotted from the finite element solution and the isochromatic lines observed in the loaded model.