PROPOSED PARAMETRIC DESIGN MODEL FOR SHEAR IN REINFORCED CONCRETE.

An ultimate limit state design model is presented for use in unusual situations of shear evaluation or for general use in explaining aspects of shear behaviour. The model specifically considers elements unreinforced for shear and the transition to elements lightly reinforced for shear in a consistent manner up to levels where the truss analogy becomes fully applicable. The model augments CP110 and BS8110 and is based on a semi-rational assessment of the observed (in tests) or visualized (in design) ultimate diagonal shear crack at failure. The evaluation of an observed ultimate failure mode in this regard has many parallels with yield line theory for flexure, in which the observed collapse mechanisms for slabs are used to quantify the ultimate collapse load. It is envisaged that the model will be used in a manner similar to yield line theory, in that both are used to undertake ultimate limit state checks on unusual structural situations.