The Riddle of Shear Failure and Its Solution.

This paper intends to answer two questions: (a) What is the internal mechanism of the so-called shear failure of a reinforced beam, and (b) What is the strength of this mechanism? Under increasing load a reinforced concrete beam transforms into a comb-like structure. In the tensile zone the flexural cracks create more or less vertical concrete teeth, while the compressive zone represents the backbone of the concrete comb. The analysis of this structural system has revealed that two rather different mechanisms are possible: as long as the capacity of the concrete teeth is not exceeded the beam-like behavior governs; after the resistance of the concrete teeth has been destroyed a tied arch, having quite different properties, remains. For both mechanisms simple analytical expressions have been developed. Tests carried out at the University of Tor onto on sever a I series of reinforced concrete beams have confirmed this theory, as did some other available test results. [ABSTRACT FROM AUTHOR]