## Driven Pile Downward Capacity

## Driven Pile Downward Capacity

(OP)

Hello,

It is my understanding that the driven pile downward capacity is the Ultimate pile capacity in Compression (please correct if I am wrong).

By following NAVFAC DM 7.02 guidance, I noticed they provide formulas for computing the allowable pile capacity (see attached).

NAVFAC does not specify a Factor of Safety when computing Qall.

Anyone knows what would be the FS in case I need to compute Q ultimate based on NAVFAC Q allowable formulas?

Thanks.

It is my understanding that the driven pile downward capacity is the Ultimate pile capacity in Compression (please correct if I am wrong).

By following NAVFAC DM 7.02 guidance, I noticed they provide formulas for computing the allowable pile capacity (see attached).

NAVFAC does not specify a Factor of Safety when computing Qall.

Anyone knows what would be the FS in case I need to compute Q ultimate based on NAVFAC Q allowable formulas?

Thanks.

## RE: Driven Pile Downward Capacity

## RE: Driven Pile Downward Capacity

The older AASHTO Standard spec used nominal loads and a capacity of 0.25Fy*A (SF=4)

Rod Smith, P.E., The artist formerly known as HotRod10

## RE: Driven Pile Downward Capacity

2 more questions:

1 - Do you understand that the downward pile capacity is the ultimate capacity?,

2 - From the file attached, the ENR formula Qall = 2 WH / (S + 1). NAVFAC specifies S (average net penetration) in inches and H (effective height of fall) in feet. Do you think that makes sense?, it is my understanding that H needs to be inches.

Please let me know,

## RE: Driven Pile Downward Capacity

1) There's the structural limit of the pile in compression, which we discussed above. That's typical for steel piles driven to refusal.

2)There's the structural limit for a pile in tension. Typically that's only reached by concrete drilled shafts in uplift, which some categorize as piles.

3) There's the geotechnical limits in bearing (resisting downward forces in end bearing and/or side friction) and uplift (side friction resisting upward loads).

For #2, I suspect the formula given is an approximation, not an actual equation, per se, so the units aren't necessarily consistent. I suppose they could have written it with a constant of 12 in the denominator and specified H in inches, but then the user would have to multiply H (which would typically be in feet) by 12 and then divide the answer by 12.

Rod Smith, P.E., The artist formerly known as HotRod10

## RE: Driven Pile Downward Capacity

## RE: Driven Pile Downward Capacity

## RE: Driven Pile Downward Capacity

Oldestguy, if you are required to compute the Q ultimate (not Qall) using the ENR formula, what would you do?,

Qall = 2 WH / (S + 1), would you remove 2 from the numerator and use H in feet and S in inches?

## RE: Driven Pile Downward Capacity

Regarding factors of safety, this reference may be helpful for non-LRFD approach, and has references to a number of informative papers: https://www.pile.com/wp-content/uploads/2017/03/14...

## RE: Driven Pile Downward Capacity

## RE: Driven Pile Downward Capacity

At one point the original article for the ENR formula was available on www.vulcanhammer.info. It is titled Piles and Pile Driving

Edit: Here is the article https://vulcanhammerinfo.files.wordpress.com/2017/...