Partial prestressing in concrete corbels and deep beams

Abstract

Reports on investigation of the effects of partial prestressing on the behavior and strength of concrete corbels and deep beams. Twenty specimens, with the degree of prestress and the shear span-to-effective depth ratio a/d as the main variables, were tested to failure. According to the test evidence, cracks initiated in these specimens at or near the section of maximum moment and the moment at cracking as well as the ultimate shear strength increased with increasing degrees of prestress. The specimens failed in either shear-compression or flexure, with the mode of failure changing from the former to the latter as the degree of prestress increased. The shear-friction theory and the ACI equations for corbels and deep beams were found to underestimate grossly the ultimate strength of the specimens. The truss (strut-and-tie) analogy, on the other hand, gives reasonable predictions of the ultimate strength within the scope of the present test program.