I don't know what the Rm lines are for, other than that they seem to be related to the balance moment, which affects the capacity reduction factor calculation in some codes (but not Eurocode 2). How does the book say it is calculated?
Incidentally, if I search for Deep Surface and the authors...
I use Onedrive because you get plenty of space as part of Office and it's reasonably easy to use, although there are plenty of things I don't like about it.
I briefly used Dropbox when it first came out, but I really dislike it and try to avoid it as far as possible.
I'd say the majority of...
Neither of those calculations have anything to do with bending moments.
For a rectangular stress block with a specified stress the force in the concrete = stress x area.
For a linear-elastic stress block we don't know the stress, but it is proportional to the distance from the neutral axis...
You should absolutely assume everything you read in this forum is wrong, until proved otherwise.
But the same applies to "official sources".
As for sources of information, rather than accepting numbers presented in chart form in a book I think it is better to work through calculation examples...
Sorry about that, you have to stop somewhere.
CSA does get a mention in this one:
https://interactiveds.com.au/Publications/Shear%20and%20Torsion-CIA-2023.pdf
What is the point of referring to old charts that will have different results to the current code?
Also being printed in a book does not make a chart "official".
I don't know of any printed interaction diagrams for the latest AS 3600, but you can always use the RCInteract function from my RC design functions spreadsheet, which you can download from:
https://newtonexcelbach.com/2025/02/08/rc-design-functions-9-07/
Also see...
The interaction diagram shown is not for biaxial loading. The examples in the book find the capacities about the X and Y axes, and then combine the ratios of applied moment to moment capacity, using the code simplified approach.
The Australian code (AS 3600) has procedures for finding the...
We are starting to go round in circles here, but:
It's "acceptable" in the sense that it will always be conservative, and will give the correct result when M = 0, but I don't see the point of doing complex calculations with a lower than required limit on the strain, when a straight line...
Frankly I am not sure how cl. 6.1(5) is supposed to be applied, but since we are not analysing a flanged beam it doesn't seem relevant anyway. There seems to be general agreement, both in the post above and in the other thread you started here, that as the NA goes from just outside the section...
No, we aren't over-estimating the in-between points. The curve if you did the calculation would be slightly convex, so a straight line would be slightly conservative, but the difference is very small.
You only get the step in the line in your graph because you insist on reducing the strain at...
Full calculation? Sure:
Force = Concrete stress x concrete area + (Es x 0.00175 - concrete stress) x steel area.
All forces are symmetrical about the concrete centroid, so moment = 0.
What do you understand by "pure compression"? My understanding is that the compression strain is constant across the section, so the bending moment is zero. Under that condition the strain limit applies across the full section. When the NA is at the base of the section the strain distribution...
