Pipeline Support Piles 1

[oilcivil]

Out here in California petroleum, we typically use 'T' supports with cast in place concrete "pile" foundations. Some supports have lateral forces but many are only providing vertical support. Right now there is a school of thought that all of the supports should have rebar cages in the foundations. I used to be of this school of thought because of temperature shrinkage control comments in the ACI 318. However I just came across a portion of the Plain Concrete section of the ACI that states that cast in place concrete piles are not really covered in the ACI. Additionally, read an old post by GeoPaveTraffic that mentioned rebar cages aren't really necessary for supports only under compression. Regardless, for a support like this, with little (friction) to no lateral forces, I'm not really seeing the need for the rebar cages. Has anyone run into this debate in the past? Are there any codes or standards one would point to? Also if the friction is an issue, couldn't something be places between the pipe and support to limit the lateral friction?

Thanks in advance

 

[BigInch]

I presume you mean the "Sonotube" type cast in place columns. Lightly loaded cast in place columns in soil can be exposed to significant tension simply if placed in expanding clay soils. If there is any slight wind load on the pipe, large tension causing bending forces in the support can be transmitted into the pile. With only a light vertical load, it is possible compressive forces may not be present across the full section allowing tension to show up on the opposite side.

You'd be far better off to include at least minimum temperature and shrinkage steel. What's that going to cost you, except a possible bad reputation if you don't. I wouldn't want to be known as the engineer that wouldn't put a few #4 in a column in earthquake territory!

I hate Windowz 8!!!!

 

[oilcivil]

Thanks for the input. Yeah just to be clear I'm talking about a 'T' support supporting a pipeline only in the vertical direction. No guides or anchors on the support. Thanks again

 

[MJCronin]

"couldn't something be places between the pipe and support to limit the lateral friction? "

http://www.pipingtech.com/products/ptpcat/slideplate/ptfe.htm

http://www.anvileps.com/_literature_117061/Guides_and_Slide

MJCronin
Sr. Process Engineer

 

[BigInch]

Yes I thought so. I've probably done more than 100,000 of them. T supports, W6x12, 3/8" base plate, 4 anchor bolts on top of a concrete filled Sonotube. My favorite method is to use a Sonotube stuck into the ground just like a fence post, usually no footing, down to the freeze level, or to the level where soil moisture is constant (4 ft or so) where the clay doesn't usually expand or contract any more. If you notice in these images, some obviously are designed for bending moment, but all have at least some rebar. Pipe on a T support will pick up wind loads and seismic loads and cause bending in the column, maximum at the base plate, which will be transmitted into the sonotube through the 4 anchor bolts. The light load from 1 or 2 pipes on top will not be enough such that the sonotube remains in compression across the full section.

https://www.google.com/search?q=son...7AaA44DQCg&sqi=2&ved=0CDwQsAQ&biw=942&bih=734

I hate Windowz 8!!!!

 

[oilcivil]

Thanks, yeah where I work in southern california there are only a handful of times a year where we get below freezing. Sometimes we use sonotubes, sometimes we don't but the foundation is always designed using the pole embedment calculation method from section 18 of the CBC. It is common knowledge that this is pretty conservative but since it is in the code it is the go to method. Then the rebar cages are almost always used as well. The cages are usually about 8 -#6's in the vertical direction and #4 hoop ties about every 12" or less. We differ in that out 'T's are made of pipe and embedded at least 2' to 4' into the concrete. The T has nelson studs on it to help it "bite" into the concrete. Regardless, we install tens of thousands a year so even eliminating small inefficiencies in the design make a big impact.
Thanks again

 

[BigInch]

Do you coat the pipe section? How are you doing with corrosion of the pipe element, or doesn't it rain enough to have corrosion there?
Drop the pipe support element nearly to the bottom of the concrete and then you could probably forget about the vertical bars.

I hate Windowz 8!!!!