RC Flanged Section
RC Flanged Section
(OP)
I am trying to calculate the nominal moment strength of the attached, but I keep getting the compression block, a = negative number. I am using
a = [(Asfy-A'sf's)/(0.85f'c)-(b-bw)hf+A's]/bw
Would you know what I might be doing wrong?
Thanks,
a = [(Asfy-A'sf's)/(0.85f'c)-(b-bw)hf+A's]/bw
Would you know what I might be doing wrong?
Thanks,






RE: RC Flanged Section
Such a problem is very fundamental and as a structural engineer or civil engineer you are expected to know how to check your work.
Regards,
![[pipe] pipe](https://www.tipmaster.com/images/pipe.gif)
Qshake
Eng-Tips Forums:Real Solutions for Real Problems Really Quick.
RE: RC Flanged Section
Next, you do not define the term 'hf'. What is that supposed to mean? Are you expecting us to be mind readers?
My advice to you is...do not simply apply formulas. Try to understand what they mean. Until you do that, your designs cannot be used in structures where human life is at stake.
BA
RE: RC Flanged Section
To start with, if the depth 1" at the top were correct, you do not have sufficient cover for corrosion protection or development of reinforcement. With 1" to the centroid of the longitudinal steel, and assuming 1/2" (#4) transverse bars at the top, your cover is 1/4", which is less than the tolerance for cover or bar placement. I have seen concrete work with approximately zero cover but it is never permitted by code.
For the example, where compression steel yield strength exceeds tension steel yield strength, it is conservative to consider the distance between the centroids of reinforcement as the moment arm. You have a tension-controlled section, and while the centroid of the theoretical compression block is located above the compression steel, engineering design is about practical design as much as it is about theoretical precision.
RE: RC Flanged Section
for flanged beams I would normally ignore the compression reinforcement and treat it as singly reinforced. It really does not make that much difference.
It is fundamentally critical that you understand the theory behind these formulii as they are only approximations of reality. They are perfectly accurate 9 out of 10 times but for that tenth one you need to understand the shortcomings of the formula to ensure its safe application.
You are also recieving a bit of sharp feedback due to your lack of attempts to help yourself. A google will bring up a huge amount of worked examples that can be followed to ensure you have the correct methodology. Good luck.
RE: RC Flanged Section