Diagonally reinforced coupling beams Upper limit - ACI-318 vs NZS-3101 1

[QSIIN]

ACI 318 has quite a stringent upper limit on maximum allowable shear stress on diagonally reinforced coupling beams [10SQRTf'c (psi) / 0.83SQRTf'c (MPa)], however the new Zealand concrete code, NZS 3101 states "No Upper limit is placed on the shear force that may be resisted by diagonally reinforced coupling beams".

NZS explains the advantage of this detailing is the high shear stress and deformation that can be accommodated, at the expense of complexity and congestion.
ACI explains test results demonstrate that diagonally reinforced coupling beams have adequate ductility at shear forces exceeding the limit, therefore the limit provides an acceptable upper limit. This doesn't make much sense to me.

Is anyone able to extrapolate or explain this in anyway?

 

[ggcdn]

You're right that the commentary appears to have a grammatical error.

A23.3 (Canada) also doesn't limit shear stress but notes that shears above 1sqrt(fc) [MPa] can lead to constructability issues.

I think the problem comes down to the fact that there simply haven't been any tests on specimens in such high shear stress. The vast majority of tests are in the 0.25sqrt(fc) to 0.83sqrt(fc) range.

-JA
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