Short Battered Piles
Short Battered Piles
(OP)
Does anyone have any ideas of why battered piles should be limited to lengths of over 15 ft? I have a few theories but I was wondering if any one had solid information on this subject.
I am currently working on a bridge project where we would like to use piles at the abutments in lieu of drilled shafts but we have only 10 feet from the bottom of the footing to bedrock (excavation to bedrock is not an option due to other site constraints).
The State's Bridge Design Manual states that piles under 15 ft in length SHOULD not be battered but there is no explanation of why.
I am currently working on a bridge project where we would like to use piles at the abutments in lieu of drilled shafts but we have only 10 feet from the bottom of the footing to bedrock (excavation to bedrock is not an option due to other site constraints).
The State's Bridge Design Manual states that piles under 15 ft in length SHOULD not be battered but there is no explanation of why.





RE: Short Battered Piles
No matter what you're state's bridge manual says, AASHTO sets a minimum steel pile length of 10'. Often, if a state agency can't get 10' naturally, they will drill out the amount(10 or more feet) with "pre-bore".
So depending on what the costs are in your area, you may wish to consider using the drilled shafts since you may have to drill the steel pile holes and seat them in with sand.
As for the greater than 15' limit, I suspect it's due to the reliable properties of the overburden at that shallow depth.
Good Luck.
Regards,

Qshake
Eng-Tips Forums:Real Solutions for Real Problems Really Quick.
RE: Short Battered Piles
I agree with your assessment of pile lengths and AASHTO Code but my question is more related to BATTERED piles. I was wondering if their ability to resist horizontal loads is compromised when their length is less than 15 ft.
As for the overburden at the site, the piles would be end bearing on rock so I wouldn't think that the overburden would be an issue.
RE: Short Battered Piles
RE: Short Battered Piles
Thanks for the clarification. That is exactly what I was trying to get across.
With a shallow bearing strata, and with the fact that most engineers dismiss the upper 10-15' as disturbed or potentially disturbed it reasons that engineers would discount the lateral confinement necessary to develop a reaction to the applied lateral load.
Regards,

Qshake
Eng-Tips Forums:Real Solutions for Real Problems Really Quick.
RE: Short Battered Piles
Thanks for your help!
RE: Short Battered Piles
cage
RE: Short Battered Piles
RE: Short Battered Piles
An array of fairly heavy tipped H piles ought work ok for what is prolly a rather smallish bridge.
Short stiff tip bearing batter piles under lateral load either buckle and fail or lift the structure as they rotate about their tips. A solution that tends to look good on paper but often not that hot. If the batters are longer and less stiff they deflect and so shed some load. But still iffy.
BSC
RE: Short Battered Piles
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RE: Short Battered Piles