How to check for maximum steel ratio
How to check for maximum steel ratio
(OP)
I have this computation for singly reinforced rectangular beam and found that
rho_max = (3/7) * 0.85 * f'c * beta_1 / fy
That is based on ACI 318 strain of tension steel of 0.004 and concrete of 0.003.
The same formula actually was posted by user JAE (Structural) in this thread: http://www.eng-tips.com/viewthread.cfm?qid=136515
However I found that in many situations, this value of rho_max will go lower than who_balance which I think is not reasonable.
Example, I have this (I am doing SI here but please disregard on that and let's just compare the results)
f'c = 21 MPa, fy = 276 MPa and beta_1 = 0.85
I have these results:
rho_balance = 0.85 * f'c * beta_1 * 600 / [ fy (600 + fy) ] = 0.03765
And for rho_max in the above formula, I get rho_max = 0.02356 only which is less than rho_balance.
So how can I check if I'm not going above maximum permissible reinforcement if using the of concrete won't get me there.
Is there anything or something that I miss or other thing that I need to look for?
rho_max = (3/7) * 0.85 * f'c * beta_1 / fy
That is based on ACI 318 strain of tension steel of 0.004 and concrete of 0.003.
The same formula actually was posted by user JAE (Structural) in this thread: http://www.eng-tips.com/viewthread.cfm?qid=136515
However I found that in many situations, this value of rho_max will go lower than who_balance which I think is not reasonable.
Example, I have this (I am doing SI here but please disregard on that and let's just compare the results)
f'c = 21 MPa, fy = 276 MPa and beta_1 = 0.85
I have these results:
rho_balance = 0.85 * f'c * beta_1 * 600 / [ fy (600 + fy) ] = 0.03765
And for rho_max in the above formula, I get rho_max = 0.02356 only which is less than rho_balance.
So how can I check if I'm not going above maximum permissible reinforcement if using the of concrete won't get me there.
Is there anything or something that I miss or other thing that I need to look for?





RE: How to check for maximum steel ratio
Now the code uses limits set by ductility. Your reduction is more if your section is less ductile. But I would still follow the old limits by either deepening or widening your section. If you're over 1.5% rethink your design.
RE: How to check for maximum steel ratio
RE: How to check for maximum steel ratio
Usually deflection or shear takes care of it on its own, but every once in a while, I end up in that range.
RE: How to check for maximum steel ratio