Thank you for sharing.

Any chance t0 have a function like PDIST in 3D?

I think I’m asking for too much.

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]]>Thanks Doug. I will keep an eye out for your paper and upcoming post.

Complicates the M-V interaction method though as you would need to filter out certain results / identify where this may apply. I suppose you design for max bending, then do M-V checks for only sections either side of max bending.

I just created a WordPress account so I can comment more easily :).

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]]>Thanks for the comment Marc,

I’m actually in the process of writing a paper for the Concrete Conference (due on Thursday) looking at provisions for shear in AS 3600 and AS 5100.

When that is finished I’ll look at doing a post on this issue, but briefly the case you outlined is not normally a problem because the additional bending steel is required at the base of the compression strut, where the moment is less than it is at the section where the shear force is applied.

The codes are not very clear about where this can and can’t be applied however, and are not consistent, so It’s worth looking at in more detail.

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]]>Very interesting post, thank you.

I’ve been thinking about M-V interaction cruves and how one might use them in practice when considering also clause 8.2.9 in AS 5100.5.

By way of example, take a simply supported beam with a generic combination of loads. You’ve gone ahead and sized your longitudinal reinforcement such that the bending utilisation is ~100% (M*~= Phi x Mu) at midspan. And for arguments sake the midspan V* is zero. All seems well thus far.

If you then proceed to plot all of the design effects (M*,V*) on the M-V interaction curve produced via the method in this post, then at points close to the maximum moment location you may start to see various “failures” as soon as V* becomes non-zero because there will be additional longitudinal steel required (and thus the bending capacity is reduced). This would seem to immediately contradict 8.2.9.2 at any cross sections considered “adjacent” to the maximum moment region (whatever that means).

If a detailed M-V is the theoretically sound approach (and I think it is), the code should probably move away from the 8.2.9 simplifications, but this would be quite a shift in thinking for designers I suspect?

Cheers.

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]]>Thanks!

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]]>For the NA angle the code has limits of +-89 degrees. For the depth of the neutral axis it first checks with the concrete entirely in compression. If that shows that the NA is inside the concrete section it checks each layer working down from the compression face to find the layer with the NA, then uses a closed form solution to find the exact depth.

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]]>Some of the older download links here need “http” to be changed to “https” to work with current browsers. I have now done that, so the link should work now, but a later version is available at:

RC Design Functions 9.03; compression strut angle adjustment

Also note that the Downloads tab at the top of the page has a spreadsheet listing all available downloads, with working links to the latest versions, and also with links to the latest blog post.

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