IBC pile question

[SteelPE]

Section 1810.3.1.3 of the 2009 IBC requires that the foundation be designed to resist the effects of mislocation of any deep foundation element by 3”. This is easily achieved in the design of the cap)…. However, how is it accounted for in the design of the piles under the cap (it does allow you to use 110% of the pile capacity in this instance)?

Does this mean that I have to design the pile group for the moment = (the column reaction) x (3 inches)? Or is the 3” accounted for in the geotechnical design of the piles (with a reduced allowable capacity)?

 

[ishvaaag]

In my view if 3" deviation is allowed, it is allowed and no excursion of the loading needs to be made; however since subject to opinion you or the revising party might want to go more conservative and proceed for everything with an excursion of the load to the allowed limits at least; that shouldn't be unreasonable.

To minimize effects on the pile design the best thing would be to make a 3D model with displaced pile and soil and then see how the soil effectively coerces the pile as to produce an almost unchanged state respect the perfectly placed pile case; it may also be helpful to assign proper reinforcement to the piles.

 

[SteelPE]

ishvaaag,

The design of the caps is the simple part. All I need to do is account for the additional moment (and possibly shear ) when I design the cap. In fact, I believe the CRSI (the standard go to book in the US for concrete design charts) accounts for the 3" eccentricity in the design of the cap. However, if you had to account for the eccentricity by moving the load then none of these charts would be acceptable as they deal with vertical load only with no eccentricity. Accounting for moment in a cap is simple but extremely tedious.

I guess I am just getting a little confused.

 

[slickdeals]

Based on previous experience, I have always received as-builts of piles and then run them really quick in my analysis program to account for the additional loads in the pile due to eccentricity.

More often than not, I have used RAM Concept to get pile loads and it gives me the option to move every pile in a pile cap relative to its original configuration.

Alternatively, you can set up a spreadsheet that does this for you.