A lot of the foundations I design are drill shaft/caissons/drilled piers. Recently, something came to my attention that I should revisit what I've been using to determine minimum longitudinal reinforcement but can't seem to find any set standards other than the ones I'm going to list below. These foundations are going to be resisting high moments.
We've been using ACI 318, 15.8.2.1 which is 0.5% of gross area. However, section 1.1.6 says that "This Code does not govern design and installation of portions of cencrete piles, drilled piers, and caissons embedded in ground except for structures assigned to Seismic Design Categories D, E, and F."
So I've been looking at other codes to see what kind of standards other people have been using for drilled piers.
The U.S. Dept of Transportation Federal Highway Administration (publication no. FHWA-NHI-10-016) says min reinforcement amount is determined by AASHTO 5.7.4.2-3 equation (As*fy)/(Ag*f'c)>= 0.135, but also states that 0.5% of gross concrete area of the pile is suggested practical minimum.
ACI 336.3R-20 doesn't go into detail on minimum steel requirement. If I missed the specific section, please let me know.
I've read through old threads on this forum and there doesn't seem to be consensus. Overall I've seen a lot of people use 0.5%-1% of gross area.
I've been using PLS-CAISSON to analyze foundations and the manual says that the steel reinforcement portion of the program is based on ACI Publication SP-7 "Ultimate Strength Design of Reinforced Concrete Columns" (1964). I got a copy of the book and can't seem to figure out how they incorporate this into the program. I found that the higher the moment, the quantity the rebar that is being asked for is not reasonable. Also if anyone can try to explain how to use the tables in this book, I would be most grateful. I want to figure out how PLS-CAISSON determines their rebar quantity and if it's something we should consider using in the future or if we should stick with what we've been using (0.5% * Ag).
We've been using ACI 318, 15.8.2.1 which is 0.5% of gross area. However, section 1.1.6 says that "This Code does not govern design and installation of portions of cencrete piles, drilled piers, and caissons embedded in ground except for structures assigned to Seismic Design Categories D, E, and F."
So I've been looking at other codes to see what kind of standards other people have been using for drilled piers.
The U.S. Dept of Transportation Federal Highway Administration (publication no. FHWA-NHI-10-016) says min reinforcement amount is determined by AASHTO 5.7.4.2-3 equation (As*fy)/(Ag*f'c)>= 0.135, but also states that 0.5% of gross concrete area of the pile is suggested practical minimum.
ACI 336.3R-20 doesn't go into detail on minimum steel requirement. If I missed the specific section, please let me know.
I've read through old threads on this forum and there doesn't seem to be consensus. Overall I've seen a lot of people use 0.5%-1% of gross area.
I've been using PLS-CAISSON to analyze foundations and the manual says that the steel reinforcement portion of the program is based on ACI Publication SP-7 "Ultimate Strength Design of Reinforced Concrete Columns" (1964). I got a copy of the book and can't seem to figure out how they incorporate this into the program. I found that the higher the moment, the quantity the rebar that is being asked for is not reasonable. Also if anyone can try to explain how to use the tables in this book, I would be most grateful. I want to figure out how PLS-CAISSON determines their rebar quantity and if it's something we should consider using in the future or if we should stick with what we've been using (0.5% * Ag).
