Some shear tests on reinforced concrete beams without shear reinforcement

Abstract

Summary Tests were made on rectangular reinforced concrete beams without shear reinforcement in order to determine the effect on shear strength of: manner and position of loading; amount and type of reinforcement; strength of concrete. The results indicate that: for short shear spans, a beam loaded directly on its top surface can sustain a load greater than that causing the formation of a major inclined crack (the diagonal cracking load), but only with considerable widening of the crack; a beam loaded through transverse beams or nibs will not sustain a load higher than the diagonal cracking load, whatever the shear span; the diagonal cracking load increases slightly with increase in the amount of longitudinal reinforcement, but is apparently little affected by the bond characteristics of the bars; the diagonal cracking load increases with increase in the strength of the concrete, but not at the rate indicated by the British Standard Code of Practice CP 114:1957. In an evaluation of the results of the tests a method is developed for estimating the diagonal cracking load of rectangular beams without shear reinforcement. From a comparison with available test data it is shown that, though the method is simple in its application, it has a fair degree of accuracy. Design recommendations based on it are given.