Foundation/Helical Pile Contractors

[TRAK.Structural]

Anyone here do work with residential foundation contractors who install helical piles and other foundation repairs? Recently I've been asked to "approve" a recommended repair scheme that was put together by one of these types of contractors. This is part of a real-estate transaction so my info has come solely from a Realtor at this point and I do intend to reach out to the contractor but I am curious how engineering consultants go about working on stuff like this. Is it as simple as calculating the applied loads in the affected area and verifying that the published capacities of the pile products can resist the loads? Would you want to observe the installation of the piles and verify measured installation torque matches the spec.? Do you typically check dimensions of the footing after it is uncovered to verify that it can span between piles? What are the major pitfalls in being the consulting engineer working to verify these types of repairs are adequate?

I use the word "approve" in the above loosely so let's try not to get hung up on what constitutes being in responsible charge etc. etc. My intent, If I take the job, would be to perform the actual engineering myself just like when I design new structures from scratch.

 

[dik]

I generally just spec them and provide the design loads. The helical pile supplier provides the sealed design.

On one project in Saskatchewan, I designed the helical piles based on information provided by the geotekkie. It was a transformer pad with six 400,000 lb transformers... my first helical pile design.

 

[XR250]

The AHJ requires us to write a "closeout letters" for our underpinning designs. We just base it off pictures and boring logs/torques.

 

[SE2607]

Anyone here do work with residential foundation contractors who install helical piles and other foundation repairs? Recently I've been asked to "approve" a recommended repair scheme that was put together by one of these types of contractors. This is part of a real-estate transaction so my info has come solely from a Realtor at this point and I do intend to reach out to the contractor but I am curious how engineering consultants go about working on stuff like this. Is it as simple as calculating the applied loads in the affected area and verifying that the published capacities of the pile products can resist the loads? Would you want to observe the installation of the piles and verify measured installation torque matches the spec.? Do you typically check dimensions of the footing after it is uncovered to verify that it can span between piles? What are the major pitfalls in being the consulting engineer working to verify these types of repairs are adequate?

I use the word "approve" in the above loosely so let's try not to get hung up on what constitutes being in responsible charge etc. etc. My intent, If I take the job, would be to perform the actual engineering myself just like when I design new structures from scratch.

I've done this type of work. In doing so, I have determined the capacities of the piles and have compared it to the demand. Here is a source:
www.ramjack.com/commercial/engineer-resources
In my cases (two story residential), the limiting factor is the capacity of the existing footing spanning between piles. One of the "issues" I've had with the specialty contractor is that, when they provide the capacities, they consider the load (applied at the centerline of the footing) to be concentric with the pile. For retrofit conditions, the pile is attached to the side of the footing with an "L" bracket. In my analyses, I apply an eccentricity, which obviously diminishes the capacity of the 2-7/8" diameter pile shaft. Still, the limiting state is the capacity of the existing footing to span between piles. IIRC, I don't get/need much more than 15k (ASD) on each pile even though the contractor claims a capacity of ~50k.
I also get pile logs and compare them with the demand.
HTH

 

[dik]

I understand that in a given area there is a close correlation between the installation torque and the load capacity.

 

[XR250]

I've done this type of work. In doing so, I have determined the capacities of the piles and have compared it to the demand. Here is a source:
www.ramjack.com/commercial/engineer-resources
In my cases (two story residential), the limiting factor is the capacity of the existing footing spanning between piles. One of the "issues" I've had with the specialty contractor is that, when they provide the capacities, they consider the load (applied at the centerline of the footing) to be concentric with the pile. For retrofit conditions, the pile is attached to the side of the footing with an "L" bracket. In my analyses, I apply an eccentricity, which obviously diminishes the capacity of the 2-7/8" diameter pile shaft. Still, the limiting state is the capacity of the existing footing to span between piles. IIRC, I don't get/need much more than 15k (ASD) on each pile even though the contractor claims a capacity of ~50k.
I also get pile logs and compare them with the demand.
HTH

We make them chip the footings flush with the foundation wall to limit eccentricity. Honestly, i don't even calc the footing capacity unless it is obviously going to be a crap one. Standard of care around here is install them 5-6 ft, O.C. and figure out the load based on that. These things have a bit of voodoo to them as I don't know how they calc out at all with the eccentricities involved but they seem to perform well. When they don't, the contractor just comes and tightens them up. That is what a lifetime warranty gets you.

 

[SE2607]

We make them chip the footings flush with the foundation wall to limit eccentricity. Honestly, i don't even calc the footing capacity unless it is obviously going to be a crap one. Standard of care around here is install them 5-6 ft, O.C. and figure out the load based on that. These things have a bit of voodoo to them as I don't know how they calc out at all with the eccentricities involved but they seem to perform well. When they don't, the contractor just comes and tightens them up. That is what a lifetime warranty gets you.

5-6 feet span of an existing footing is about what I get analytically.

 

[XR250]

Don't forget to take into account some arching action of the foundation wall if it ain't too beat up.

 

[TRAK.Structural]

Dik - When you say the "supplier" are you saying the contractor provides a sealed design for the piles themselves, or they have the pile manufacturer provide a seal?

XR - do you typically have some test pits dug first to determine if its going to be a "crap one" by looking at its condition/size?

SE2607 - For 2-story construction do you require cutting drywall/ceiling to figure where the load bearing elements are so you can track the load down? For 1-story stuff I think conservative assumptions work fine but could see that getting out of hand for larger homes.