Battered piles in tension

[scarr1]

I am designing a 7 story concrete building. Lateral system: shear walls. Foundations: Micropiles. I have huge lateral loads on this structure because: 1. I am holding back 20' of earth on two sides (non-opposite sides). 2. The structure is highly irregular and stiff (high seismic loads).

I want to use battered piles to resist the lateral loads under the shear walls. My geotech report says that I can use the horizontal component of the pile's axial capacity to resist lateral loads. Would it be more correct to use the horizontal componant of the axial load that is actually acting on the pile at the time of the shear load as resistance for the lateral?

Also, the piles can be designed to resist about half of their axial capacity in tension. If i batter the piles away from the direction of the shear, can i use the pile in tension (once vertical loads have been overcome) to resist the lateral loads. Wouldn't it be more efficient to batter the piles in this way (tension) because then the vertical loads on the pile are actually off-setting the tension imposed by the lateral loads?

Thank you for your help.

 

[miecz]

Yes and yes. The horizontal resistance of the battered pile depends on the calculated axial force. Think of the Geotech's recommendation as the upper limit of this resistance. We have used micropiles battered away from the direction of the shear, in tension, to resist lateral forces. It seems more efficient to me. FHWA published "Micropile Design and Construction" in June, 2000 (FHWA-SA-97-070).