Casting Bolts in Reinforced Concrete foundation 2

[010185]

A foundation on which a pylon is to be built so that the pylon structure can be placed directly onto it once it's completed.

On the top surface of the foundation (Surface area = 4.5m x 4.5m) 24 holding down BOLTS of length 1000mm are to be CAST VERTICALLY with 800mm of their lengths into the concrete.

The finished LEVEL OF BASE IS TO ACCURATELY ALIGN with the floor of the pylon and the tolerance is +/-3mm.

The location of the bolts is critical; there is only +/-2mm clearance in the pylon bases and all bolts must be 100% vertical.

Can anyone suggest a method of construction which ensures the requirements?

 

[JAE]

Usually a contractor will use a plywood template placed over the top of the concrete foundation. The plywood has slots or holes cut into it at exact locations for the anchor bolts.

The anchor bolt assembly is then placed through the template and secured below to the reinforcing bars within the concrete.

Sometimes there are supplemental steel bars, plates, or other elements that are attached to the bolts near their bottom heads to allow vertical alignments to be controlled.

I've also seen a sort of ring plate (looks like a circular ring with holes cut through for the bolts - a giant common washer plate, that helps align the bolts but allows the concrete to be placed through the ring.

 

[COEngineeer]

Just use acrylic or epoxy with all thread rod.

 

[COEngineeer]

I just realized how long your bolts are. I guess if you do use acrylic or epoxy anchor, you need to make sure there is not rebar in the way but I think you can put the bolts more accurately and straighter.

 

[010185]

Many thanks! How are epoxy anchors used though?

 

[JAE]

Drilling 800mm (31.5 inches) is a long way to drill for epoxy (as COEngineeer indicated)

One other concept that I've seen used is to cast the bolts into the concrete but sleeve the top 3/4 of the embedded portion to allow future, minor bending adjustments to the bolt if they are offset slightly. But your embedment would still need to meet the design loads so the bolts would have to be longer to accommodate this. After setting, the sleeves are grouted solid.

 

[COEngineeer]

I am pretty sure if you need to embed it 800 mm, you will probably use a fairly large diameter diameter rod or the steel will yield before you can even pull it out. How big of bolt are we talking about here? Maybe 800 mm is too deep since your bolt might yield before you can pull out the bolt.

You use epoxy or arcrylic only if you dont have temparature more than 160F environment or it will start melting and destroy they polymer. You pretty much drill a hole the same diameter as your all thread rod, brush it off (make sure all the concrete pieces is out of the hole), then blow it with air. Acrylic can set pretty quick and you can use it at cold temparature. Epoxy is harder to use if you are in cold environment plus it takes longer to harden. Pretty much like gluing the rod into the hole. Check out simpsonanchors.com for more info.

 

[dik]

Can you use oversized holes in the base plate? There's also a small diameter corregated sleeve that can be cast into the concrete and the anchor rods cast into this. This can provide for adjustment.

Dik

 

[DRC1]

For large bolts in tight tolerance patterns, steel templates are frequently used. Both top and bottom templates should be used. The top template is double nutted to the bolts. The bolts are either headed with the bottom tempates welded to the heads or threaded on each end with the top and bottom templates by double nutting.Be sure to use top & bottom templates to maintain vertically. Top templates are welded to steel supports to maitain alignment. Be sure to size the supports to sufficiently stiff to minimize deflections.

 

[010185]

The bolts are HD bolts - M40.