Abstract

In the design of reinforced concrete members, the concrete geometry and amount of reinforcement provided must be selected such that the externally applied shear force, axial force, and moment can be safely resisted. For flexure and axial loads, there is essentially universal unanimity on the “plane sections” rule while for shear, there is no global consensus on how shear is carried or what a safe set of shear provisions should look like. Through the testing of large-scale experiments and the application of the Modified Compression Field Theory (MCFT), it has been possible to develop rational and general shear design methods in Canada over the past 30 years. These provisions were sometimes criticized as being too complex for day-to-day use in building design, however. The 2004 Canadian design provisions for shear and torsion represent a breakthrough in ease-of-use while still maintaining the generality of being derived from a theoretical basis. As an example of the generality, the provisions for as derived for steel reinforced members provide conservative results when compared to FRP reinforced members as well. In this presentation, the theoretical background to the new CSA provisions will be explained, comparisons to experiments will be made, and implications to design will also be explored. It is hoped that these new shear provisions will help in the development of a consensus towards a new general, international shear design model. This may allow the confidence engineers currently feel about flexural behaviour to apply to shear behaviour as well.