Design for punching shear in concrete: critical review of Canadian Standard CSA-A23.3-94: Reply

Abstract

For punching shear design of slabs without beams, Canadian standards CSA-A23.3-94 and CAN3-A23.3-M84 require the effects of transfer of shearing force Vf and moment Mf be considered in the calculation of the shear stress vf at the critical sections at distance d/2 away from column faces and at distance d/2 from the face of thicker slab portion (drop panel). The new Section 13.4.7.5 in A23.3-94 allows, for the same calculation, to ignore the effect of Mf when considering the critical section at d/2 outside the shear-reinforced zone. The explanatory notes published (CPCA 1995) with the Standard do not explain why Mf can be ignored in the latter critical section which commonly is situated not as close nor as far from the column faces as the other two critical sections, where Mf cannot be ignored. The authors in their article stated that no published analytical or experimental work could be traced to justify ignoring the moment transfer. Thus, it was feared that the new Section 13.4.7.5 had no basis. The discussers, who are members of the code committee who introduced the new section, failed in their discussion to indicate the basis of the new section. Instead, they argue that the preceding Standard A23.3-M84, implicitly, allowed ignoring the effect of Mf for the section outside the shear-reinforced zone. Obviously, their interpretation of the Standard is not