Shear strength in the new Eurocode 2. A step forward?

The shear strength of reinforced concrete beams with stirrups has been a highly controversial matter since Ritter and Mörsh proposed the first truss models. Since then, different analytical models have been discussed, such as truss models with concrete contribution, shear/compression theories, truss models with variable angle of inclination, and compression field theories. However, some of these models were too complex to be implemented in a code of practice and they had to be simplified. As Regan has pointed out, for simpler models the problem is mostly that of the need to neglect some factors, considered secondaries. However, what is secondary in one case may be primary in another. With the release of the new Eurocode 2 (prEN 1992-1-1:2003) the controversy has been raised again. The EC-2 proposes a very simple formulation based on a truss model. However, the authors think that it is a gross oversimplification of a complex problem as it neglects important key variables. In this paper the new EC-2 shear procedure predictions are compared to empirical tests and to other simplified formulations. It is concluded that the EC-2 procedure is very easy to use by practising engineers but it presents a great scatter of results. On the one hand, it may be too conservative for slightly shear-reinforced beams or for prestressed beams. On the other, it may be slightly unconservative for heavily reinforced members.