Assessment of the flexural capacity of RC beam/column elements allowing for 3d effects

The paper describes an experimental investigation of the deformational response and the stress conditions developing in the compressive zone of reinforced concrete beam-like structural elements in bending and bending combined with axial force. The results obtained confirm the findings of earlier work and demonstrate that the compressive zone at its ultimate-limit state is characterised by the development of triaxial rather than uniaxial–as widely considered–stress conditions. These findings form the basis for introducing a simple modification in the method currently used for calculating flexural capacity and it is shown that, by complementing the proposed method with an approach that takes into account the effect of yielding of the compression reinforcement on structural behaviour, it is possible to achieve predictions of flexural capacity which are considerably closer to experimentally established values than the values obtained through the use of currently adopted methods.

► The work shows that the compressive zone of RC beams in flexure is characterised by triaxial stress conditions.
► This finding forms the basis for introducing a simple modification in the method currently used for calculating flexural capacity.
► The resulting method leads to a significant improvement of the predicted values.
► Such values contribute towards improving the margin of safety against the occurrence of brittle types of failure.