Reappraisal of methods for calculating flexural capacity of reinforced concrete members

A comparison between the predicted and experimentally-established behaviour of over 150 reinforced-concrete beam specimens (selected from 465 test results considered) revealed that around 20% of the specimens exhibited a shear, rather than the expected flexural, mode of failure. The work presented herein investigates the possibility that the causes of shear failure reflect the shortcomings of the code methods adopted for calculating flexural capacity. It is found that the predicted values of flexural capacity tend to underestimate their experimentally-established counterparts, by up to 17% on average. It is shown that by accounting for the triaxial stress conditions invariably developing in the compressive zone through a simple modification of code proposed stress blocks, the correlation between predicted and experimental values is similar to the best possible one resulting from the development and use of an artificial neural network model.