## Bending Stress in Battered Micropiles

## Bending Stress in Battered Micropiles

(OP)

I'm working on a project using vertical and battered micropiles to support a bridge pier. The lateral load of the pier is designed to be taken by the batter of the piles. In the most recent design runs the worst case ratio is roughly 15 K load vs 70 K resistance factored using the horizontal component per battered micropile. The design program was set use 0% of vertical piles for lateral resistance. My question is: Will there be a bending moment on the battered piles? Do I need to check the bending stress capacity of the micropile itself? The max. axial load is around 115 K. The micropiles are 9 5/8" casing with a #20 bar (2.5" OD)

Thanks

Thanks

## RE: Bending Stress in Battered Micropiles

www.PeirceEngineering.com

## RE: Bending Stress in Battered Micropiles

## RE: Bending Stress in Battered Micropiles

Pile Design and Construction Practice. I'll get you a quote in a while.www.PeirceEngineering.com

## RE: Bending Stress in Battered Micropiles

"For economy, the raking piles should be installed at the largest possible angle from the vertical. This depends on the type of pile used. (see 3.4.10). Where raking piles are embedded in fill which is settling under its own weight (Fig. 6.55a) or in compressible clay subjected to a surcharge load or to superimposed fill (Fig. 6.55b) the vertical loading on the upper surface of the rakers may induce high bending moments in the pile shaft. Because of this, raking piles may not be an appropriate form of construction in deep fill or compressible layers."

www.PeirceEngineering.com

## RE: Bending Stress in Battered Micropiles

## RE: Bending Stress in Battered Micropiles

www.PeirceEngineering.com

## RE: Bending Stress in Battered Micropiles

5.19.4 Battered Micropiles

The lateral load-carrying capacity of individual vertical micropiles is limited compared to

more conventional drilled shafts and driven piles. As for other deep foundation systems,

micropiles can be battered as a means to provide additional resistance to lateral loading.

Note that since micropile drilling equipment is designed to drill both vertically and

subvertically, there is not a significant increase in cost (on a per unit length basis) or quality

of finished pile for battered micropiles as compared to vertical micropiles.

The calculation of lateral capacity of a single battered micropile is demonstrated in SampleProblem No. 1.

The total lateral capacity of the battered micropiles is the sum of the lateralcapacities of each battered micropile. This lateral capacity is compared to the lateral load

applied to the foundation from the superstructure. If this sum is less than the lateral load

applied to the foundation, the remaining load is carried by the micropiles in bending (i.e., this

remaining load is used in a lateral load (i.e., LPILE analysis) for the structure).

Moreover, battered micropiles should not be used where the potential for ground

settlement around the battered micropile is a possibility. These settlements will induce

additional bending moments in the micropiles and some loss of support. Additional

discussion on batter piles for seismic regions is discussed in Section 5.21.

www.PeirceEngineering.com