Abstract:
Both theoretical and experimental studies on strength resistance of cracked RC concrete elements become complicated due to significant material anisotropy and changes in "stress - deformation" relationship for cracked concrete. Despite the fact that cracks are usually formed normally to principal tensile stresses in concrete, their further opening may not always coincide with their direction, resulting in additional shear stresses and transmission of the forces across the cracks through mechanisms of aggregate interlock in concrete and dowel/tension effects in the reinforcement crossing the crack. A better understanding of these mechanisms may be obtained through the reliable data on the relationship between stresses and displacements in sections containing the cracks. The paper presents the results of an experimental program on testing of push-off specimens made from normal, lightweight and high strength concrete. Crack behavior have been studied on three series of specimens with regard to the influence of aggregate type, concrete strength, initial crack width and amount of crossing reinforcement on ultimate shear strength and stiffness of specimen. Sets of experimental graphs have been received to show the relation between normal and shear stresses and displacements in crack faces. Working expression has been proposed to approximate experimental data. Experimental study of RC beams of rectangular section without shear reinforcement and the development of the strength model for beams under shear. Equations for ultimate strength assesment of RC beams are given allowing for effects of both aggregate interlock in cracks and dowel action of main reinforcement. The model developed fairly approximates experimental data.
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