Structural Design of Restrictor Wall inside of Existing Reinforced Concrete Pipe

[oengineer]

I have been assigned to design a restrictor wall inside an existing RCP.

Here is an example image of the task I have been given:

I am seeking some guidance about how to tackle this assignment. I have never preformed structural designs for brick.

I imagine that I need to design the brick to resist the hydro static loads acting on it when water is flowing through the pipe. Are there any design examples to for this situation?

Suggestions/comments are appreciated.

 

[oengineer]

Is there a reliable structural brick design code/reference to handle this application?

 

[phamENG]

Do you have flow data on the pipe? Velocities at various levels, etc. The straight forward requirement would be assuming the pipe is full on the upstream side and empty on the downstream (clog in your restrictor) - but the head you use is not all that easy to calculate. If this is a gravity storm pipe, the head will actually be the standing water level above grade (if water has the ability to stand above grade - it does where I am). You'll need to talk with the civil engineer to determine worst case design scenarios - these will be statistically driven.

 

[phamENG]

Yes - check the contract requirements to see what standards you're required to follow. It might be listed there. Or it may be a reference in one of them. If this were a building, I'd point you to ACI 530. You may end up there anyway, but as this could be a public utility project, there might be other requirements you have to consider. Check with your boss - they'll know the contract requirements.

 

[oengineer]

Do you have flow data on the pipe? Velocities at various levels, etc. The straight forward requirement would be assuming the pipe is full on the upstream side and empty on the downstream (clog in your restrictor) - but the head you use is not all that easy to calculate. If this is a gravity storm pipe, the head will actually be the standing water level above grade (if water has the ability to stand above grade - it does where I am). You'll need to talk with the civil engineer to determine worst case design scenarios - these will be statistically driven.

I am working on obtaining the information.

 

[oengineer]

Yes - check the contract requirements to see what standards you're required to follow. It might be listed there. Or it may be a reference in one of them. If this were a building, I'd point you to ACI 530. You may end up there anyway, but as this could be a public utility project, there might be other requirements you have to consider. Check with your boss - they'll know the contract requirements.

Would ACI 530 be applicable for this type of situation? I ask since ACI 530 has more to do with Masonary. Are you aware of any design example for this type of design, using brick?

 

[phamENG]

Brick is masonry.

 

[phamENG]

While I'm certain brick can be made to work, what kind of access restrictions are there? What about drilling and epoxying rebar and shotcreting it? Incorporate a hyrdophylic water stop along the perimeter and it seems like a better plan. Of course, drilling into the precast pipe may be a bad idea - depends on what it is and how thick the walls are.

 

[BridgeSmith]

Installing anchors and reinforcement, installing forms, and pumping grout in to create a concrete wall seems like a much more reliable solution than brickwork.

Alternately, the shotcreting approach suggested by phamENG is also a good option.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[oengineer]

Installing anchors and reinforcement, installing forms, and pumping grout in to create a concrete wall seems like a much more reliable solution than brickwork.

Alternately, the shotcreting approach suggested by phamENG is also a good option.

If I was to use just regular Reinforced CMU block walls, would it be the same design procedure as a regular wall. I ask since the CMU wall would need to be round. Does the Masonry code mention anything about circular wall designs?

 

[phamENG]

The mason will hate you. Trying to cut CMU to that profile would be a royal pain. Bricks, due to their smaller form factor, are better if you're stuck with masonry as the gaps left around the edges are small enough to be packed with mortar. But trying to build a round reinforced masonry wall inside a pipe is not a good idea.

 

[oengineer]

The mason will hate you. Trying to cut CMU to that profile would be a royal pain. Bricks, due to their smaller form factor, are better if you're stuck with masonry as the gaps left around the edges are small enough to be packed with mortar. But trying to build a round reinforced masonry wall inside a pipe is not a good idea.

So, are you saying that I should reinforce the brick? You mentioned reinforcement in a previous post.

Once I have the forces, how would I go about ensuring that the brick can handle the loads?

 

[BridgeSmith]

The mason will hate you.

I'll second that sentiment. Not only would it be a royal pain to trim the blocks, it will nearly impossible to get the reinforcing inside the blocks, or get the blocks over the reinforcing. I can't visualize a way that it's physically possible to accomplish a reinforced CMU wall in a pipe.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[phamENG]

Rod - you could pull it off with H-blocks, but that's about the only way. Grouting would still be a bit of a head scratcher.

oengineer - I did mention reinforcement. That was in reference to using shotcrete.

 

[oengineer]

oengineer - I did mention reinforcement. That was in reference to using shotcrete.

Okay. If I used shotcrete, then I could design the plug/restrictor like a Reinforced Concrete Wall with reinforcement, correct?

Also, how are the restrictors typically installed into the pipes? Are they doweled into the existing pipes?

 

[phamENG]

Yes. Shotcrete is concrete - just applied through a pressurized hose and has an essentially zero slump.

I don't deal with sewers very often. Most of the details I've seen have galvanized plate at manholes or distribution boxes, so you have a surface to bolt a plate to in order and partially cover the pipe opening, allowing you to restrict flow. So the filling in the middle of a pipe is new to me. But the way I've described it is how I would tackle the problem.

 

[BridgeSmith]

Are they doweled into the existing pipes?

You'd presumably need some type of shear pin (rebar, bolts, etc.) set in holes drilled into the wall of the pipe, either anchored with adhesive or employing some type of wedge anchor.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[oengineer]

@BridgeSmith & phamENG

If I was to just design the brick to take the hydro loads, would I just design them as non-reinforced masonry?

 

[BridgeSmith]

If I used shotcrete, then I could design the plug/restrictor like a Reinforced Concrete Wall with reinforcement, correct?

Yep. Shotcrete is 'sprayed' into place, rather than poured or pumped, but it's concrete all the same.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[phamENG]

As long as you don't reinforce it