Auger CIP Pile Design
Auger CIP Pile Design
(OP)
I need to design an auger CIP pile (12" diameter per geotechnical report), and I have never designed one before. Is there a design reference book/manual available - per ACI guidelines? How do I start?
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RE: Auger CIP Pile Design
RE: Auger CIP Pile Design
If they have only axial load there isn't much to it. What is your loading condition?
RE: Auger CIP Pile Design
Every Problem is an Opportunity for Engineers!!!!
RE: Auger CIP Pile Design
I wouldn't even consider an allowable load of 200kips on a 12" pier. Use a bigger pier.
RE: Auger CIP Pile Design
Here's a link to a publication produced by the Federal Highway Administration on design of augered concrete piles. Not a bad start for you.
Augered Cast-in-Place Concrete Piles
RE: Auger CIP Pile Design
100 tons sounds extreme for 12" pile. You should definitely require a load test!
RE: Auger CIP Pile Design
Every Problem is an Opportunity for Engineers!!!!
RE: Auger CIP Pile Design
Augercast piles derive most if not all of their resistance through skin friction, not end bearing. They don't need to be designed as columns. Quoting from the Record No. 1447 article "Managing the Installation of Augered Cast-In-Place Piles" regarding reinforcing steel:
"ACIP piles can be reinforced to resist lateral forces and to increase axial compression or tension capacity. The most common reinforcement is a single steel bar introduced into the pile immediately after casting and penetrates to the bottom of the pile. Centralizers are required to be certain that the bar remains within the pile section. Less common is introducing the bar through the hollow stem as grouting begins. A bar that is at or neqar the center of the pile has only a modest effect on the bending resistance but can provide significant tension capacity if adequate bond strength is available.
Bending strength can be provided readily by introducing a reinforcing cage or a steel member like a lightweight H section or a pipe into the pile just after grouting has been completed and before the grout has set. These sections also require centralizers to ensure they remain within the grout section as they are pushed into place. In general, there has been limited success pushing steel sections or cages to depths greater than 20 ft (6 m). Ordinarily this depth is sufficient to reinforce the pile against horizontal forces applied at the ground surface, but a shoirter depth limits the usefulness of the ACIP pile for use in cantilevered retaining structures that are more than 10 ft (3 m)to 15 ft (4.5 m) high."
I've used 12" augercast piles here in Florida, using a single #8 bar as the central reinforcment. The centralizer referenced in the article is commonly known as a "football". I would consult your geotechnical engineer regarding lateral bending, in order to determine the size of your cage or steel member (I use cages). Based on your required lateral capacity, he can run LPILE for you to determine bending moments and the required depth of reinforcement.
I agree with the others that 12" is too small for 100 tons. My guess is more like 18" to 20" diameter.
RE: Auger CIP Pile Design
Every Problem is an Opportunity for Engineers!!!!
RE: Auger CIP Pile Design
Unless you are bearing on rock at the base, 12" seems doubtful. Even then I would think you would need a bell.
Brad
RE: Auger CIP Pile Design
If no lateral load, there is only axial compression or tension, pile shaft has no bending moment.
If there is lateral load, pile shaft has bending moment, you need a *permanent* pipe sleeve for pile shaft moment resistance. Without pipe sleeve, the pile with center DYWIDAG Bar has zero moment resistance.
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RE: Auger CIP Pile Design
RE: Auger CIP Pile Design
Every Problem is an Opportunity for Engineers!!!!
RE: Auger CIP Pile Design
RE: Auger CIP Pile Design
As a starting point, you may refer to IBC. IBC 2006, section 1810.3.1 restricts allowable design stress in concrete of augered uncased piles to 33 percent of 28-day specified comp. strength, the allowable comp. stress in reinforcement to 40 percent of fy.