Experimental Study On The Damage Progress Of Concrete Beams Under The Shearing-stress

The damage and crack propagation in concrete and concrete structure has evolvedconsiderably in the past years. In this presentation, different types of boundary conditions, ie.With freely rotating, fixed or constrained loading support, of concrete damage behavior areinvestigated.Several tests are conducted in which the concrete specimens are divided into two groups：the single-edge notched(SEN) and the double-edge notched(DEN) concrete beams.Both of the two groups of specimens are loaded under four point shear force. The wholefailure process of the specimens is shot with charge coupled device (CCD). From the speckleimages，different failure phenomena are seen including the propagation paths of cracks and finalfailure mode. The speckle images captured by the CCD are manipulated from which thedisplacement，strain and shear fields in strain horizontal and vertical directions in the surface ofspecimens are gained. Among the speckle images，some are selected at certain intervals andcompared with that before deformation in order to obtain displacement and strain fields. Theevolution process of each field is gained by arranged those fields to the time order. Comparingthe displacement and strain fields gained at the place where the cracks start，it is shown that themagnitude of the horizontal and vertical displacements are close，and the values of the horizontaland vertical strains are in the same grade. The results demonstrate that the shear stress is notdominant in the zone near the notches.