Deep Foundation Elements - Allowable Material Stresses

[azcats]

I'm working on sign structure. Usual telescoping pipes that support a sign face up high. Ideal foundation for this site is a drilled shaft where the pipe is inserted and the annulus filled with concrete. Foundation design works even if I use the pipe diameter for foundation design and assume the concrete acts as soil improvement only. So that being said, the pipe is my structural element in the foundation.

How does 2012 IBC section and table 1810.3.2.6 apply here? Are the limits therein the due to axial loads only? Or does the maximum allowable stress include bending, shear, axial and torsion? If it's all combined stresses, it's really limiting if I have to design all the way down to .35Fy.

My gut says it's intended for compressive stresses only...but my gut has been wrong before.

Thoughts welcome.

 

[EZBuilding]

azcats,

This thread has some information similar to your question:

https://www.eng-tips.com/viewthread.cfm?qid=417446

Typically, I utilize the values from the table for any axial load requirements. If the deep foundation element has any bending or shear forces; I design the element based upon conventional strength design.