Concrete Barrier vs. Junction Boxes

[moskey]

We are going to be slipforming highway median barrier with electrical junction boxes embedded in the side every 500' or so. The reinforcement and electrical conduit are layed on the ground in front of the slipform machine and are picked up and fed into place by flutes out front (there is no vertical reiforcement).Here's my problem: how do we place the j-boxes in the form with out disrupting the pour? Has anybody else encountered this issue? I have attached a cross-section of the barrier and a j-box. Any input is highly appreciated.Thank you.

 

[bimr]

Junction boxes installed in structures constructed by slip forming are NEMA 3X and are adjustable for depth, with depth adjustment bolts, which are accessible from the front face of the junction box with the lid installed.

The conduit and junction boxes are usually tied onto the rebar prior to the slip forming of the concrete.

See the link and pictures 32 & 35:

http://www.wsdot.wa.gov/NR/rdonlyre...icalConduitinBbridgesandStructures1072004.pdf

 

[moskey]

bimr,

I understand that. If you re-read my post, I mentioned that the rebar and conduits are layed on the ground in front of the pour. The bar is NOT tied in place and there is no vertical bar. This is why we are having the issue.

 

[coloeng]

moskey,

Is there room behind the flutes of the slip form machine that you could stop every 500 feet, install the box and then continue slip forming? The other option would be to go in right behind the slip form and dig back into the freshly placed concrete, install the box and then grout around the hole made to install the box.

 

[bimr]

You will probably have to use a different type of slip forming machine.

http://www.gomaco.com/resources/worldstories/world34_2/photos/university/001-2613.jpg

As you can see from the picture, the reinforcing wire is probably achored at the beginning of the pour as the slip forming machine pulls away from the anchoring point. That method is not a suitable installation technique for installation of conduit or junction boxes.

Gomaco makes the slip forming machine. Perhaps you can put the question to Gomaco U.

http://www.gomaco.com/resources/worldstories/world34_2/university.html

http://www.hubbellpowersystems.com/literature/enclosures/QZ-11.pdf

 

[bimr]

Here are some links to animations showing how barrier wall slip forming is accomplished. With the machine that uses reinforcing wire, the conduit is installed either before or after the concrete slip forming, not during the slip forming.

http://www.concretebarrier.org.uk/construction/animations/embedded/embedded-wide.html

http://www.concretebarrier.org.uk/construction/animations/embedded/embedded-wide.html

http://www.concretebarrier.org.uk/construction/animations/embedded/embedded-two-barriers.html

If you desire to install conduit during the slip forming process, you will have to have a different slip forming machine and use reiinforcing bars not wire.