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.
