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Thrust Block 1

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EntryLevelEIT

Structural
Jun 24, 2010
42
Anyone have any experience with thrust blocks, codes, tips, advice?
I've been asked to design one and honestly don't know where to start besides the location and size of the pipe and where the pad should be placed.

Thanks for any help.
 
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I have been in the field when we had to excavate around them.
From what I have seen, they were just giant blocks of concrete poured around pipes where the pipe changed direction.
 
I've never seen one designed - just specified as some minimum volume of concrete at a bend in pressure pipe - usually DI.

You could specify retainer glands and save yourself the trouble..

Or for a block I'd just specify half a yard of concrete over and on the outside of the fitting, and make sure they put poly over it.
 
I have designed them only once. Basically they are giant conc masses around pipes to avoid sliding/movement of the pipe, typically located at bends or diameter changes. Get the forces from processing or MEP guys.

As for design, use passive pressure of soil to resist but here is a tip. Since the soil that you are going to using for passive will be most likely disturbed as you are going to pouring the block, use half the recommended value as your passive pressure.

You may also end up with a joint where you have you have uplift, in which case just use the weight of the conc to resist.
 
I said giant conc masses because the pipes I was dealing with were 72" dia.
 
The DIPRA downloads are available at this site:


It is not just a matter of dumping in an arbitrary amount of concrete. Thrust blocks should be designed to resist the forces involved. For that, you will need a soil investigation to provide safe bearing values.

BA
 
BA, this made me smile for some reason-
"It is not just a matter of dumping in an arbitrary amount of concrete"

Oh, IF ONLY structural engineering were that. Well, wait a minute, we would not be needed then....
 
I've designed thrust blocks on a few projects and seen a few more designed. You really need to give a bit more information though. There are difference in what the design may ential depending on pipe size, pressures, bend directions, whether the pipe is free standing or buried, where the location is etc.

Many of the ones I have seen were not simply big blocks of concrete. A lot of them included rock anchors or similar due to uplift concerns or desire to reduce the amount of concrete. Consideration should be given to adding rubber gaskets at each end of the block to reduce prying forces depending on the situation.
 
This particular thrust block got called out in the design set but was never detailed. The contractor has now pointed this out via. RFI. Just to include a few more detials:
-This is inside a new pumping station (not in service yet)
-The slab has already been poured
-The resistance is for a 30" discharge pipe
-The location is at a 90 degree turn where the pipe exits the building.

I will continue to research per everyones advice.
Thanks!
 
EntrylevelEIT,

There have been a few threads on this topic in the civils forum, I suggest you look there.
 
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