Laterally loaded pile's tip elevation 3

[tipsabc]

Any other requirements in determining the laterally loaded pile or caisson's tip elevation except considering the lateral deflection at pile cap and pile capacity? Are there any requirements for the lateral deflection shape around pile tip or moment diagram shape around pile tip? Thank you very much.

 

[Panars]

You may need to consider your superstructure requirements.
I have had structural engineers that want the bottom of the pile to be "fixed". In these cases, I would set the length equal to the depth of the second inflection point in a graph of the pile displacement.

Peter Narsavage
Columbus, Ohio

 

[GeoPaveTraffic]

I would always design the tip of the pile so that the analysis predicted no movement of the pile tip, i.e. the pile should be long enough so that the tip is fixed.

 

[Orfilos]

You need to be checking that is able to cope with all possible installation problems!, that is working under the expected mode of failure with a variation of loading effects and soil parameters(undertake sensitivity).
Always design the pile for 2-3diameters below the fixity point(zero displacemts), even if you capacity checking does not need it.
Understand the effective moduli profiles (especially if you might undergo undrained loading - dynamic soil proporties considerations. Consider the distribution of the load transfer and shear especially. Check if the piles are susceptable to lateral spreading conditions, or you have a clay layer overlying a liquifiable sand or sloping conditions. Undertake a reliable buckling checking, don't go over L/D>50. Introduce any kinematic or interaction effects. Use beam-column analyses for the pile and p-y curves for soil. If soil is silt, silty sand and clayey sand use cohesive p-y curves. If you drive the piles be very careful with your assumptions, be conservative.

 

[Focht3]

Hmmm,

You never indicated what type of structure that you are concerned about. Office buildings have one set of concerns; transmission towers for high voltage power lines are quite different. (Industry expectations and acceptable consequences of failure cause the major differences.)

I use p-y curves for lateral load analyses. Please consider my comments in that light. Other design methods may require different approaches.

I used to follow [blue]GeoPaveTraffic[/blue]'s approach; but it often runs counter to project economics - and can result in other "less reliable" foundation solutions being chosen on the basis of cost. I now focus on acceptable groundline deflection and rotation, and check for stability at twice the design lateral load.



Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora. See faq158-922 for recommendations regarding the question, "How Do You Evaluate Fill Settlement Beneath Structures?"