Grouting steel columns

[Hitch]

Need to grout some columns in, got some kwixset. in for it.

The plates will be visible, and in a public place, so needs to be neat.

Best way, to trowel it under and smooth off level with the outside of the plate? Or put a former round an inch or two away from the edge of the baseplate, and mix runny and pour? Would have a vulnerable edge on it though i think.

 

[brightspark]

Need to grout some columns in, got some kwixset. in for it.

The plates will be visible, and in a public place, so needs to be neat.

Best way, to trowel it under and smooth off level with the outside of the plate? Or put a former round an inch or two away from the edge of the baseplate, and mix runny and pour? Would have a vulnerable edge on it though i think.

trowel it under and when nearly set rub it up with a damp sponge

 

[Welderpaul]

An option to put a hole in the baseplate 50mm or so diameter?... fix timbers or box section tight to the outside of the baseplate with steel banding, then pour in? Bead of cheapo silicone to stop it running out. Makes for a neater job, with no edge likely to get chipped.
It sags like a bungle if you try to trowel it it - also risk that voids are present under the plate. Difficult to get to look right within an acceptable timescale.
Fosroc Conbextra is better stuff, or even 5 star

 

[cookie munsta]

I wouldn't mix it too wet, I'd just grout under bring it out ten mm or so from edge of base plate and put an nice mitre on the top edge to finish at the base plate. grout would need to be a workable consistancy if it gets too dry splash some water on it. should just need a trowel and some water oh and grout hope it helps

 

[stormin]

The idea of grout is that you get full bearing between the base plate and the foundation, not just relying on the packing shims. Anything bigger than 200mm square and a base plate should really have a hole for grouting. The grout should be runny enough to pour or inject to ensure no voids beneath the plate. This means some sort of former is going to be required around the edge of the plates. Clay does a fantastic job of sealing the edges.
Depends on how keen the site engineer is what you can get away with I suppose but that's the proper way of grouting.

 

[Hitch]

As i thought, trouble is getting in in there, trowel a shed load under nice and tight then, hope it doesnt slump out again. I suppose trowel it in there using 3sided former to stop it pushing back out.

Putting big holes in the plates, nice idea, never seen that on anything before though...?

 

[Welderpaul]

As i thought, trouble is getting in in there, trowel a shed load under nice and tight then, hope it doesnt slump out again. I suppose trowel it in there using 3sided former to stop it pushing back out.

Putting big holes in the plates, nice idea, never seen that on anything before though...?

Don't think you can ever guarantee no voids under the plate, even if you shove it in from one end. It just seems to keep on slumping.

Grout holes are specified fairly regularly for larger bp's. Engineers like them. If we are grouting, we put them on the smaller bp's too. Nicely in the web of a UC, or to one side of a SHS column. Saves so much messing about - just mix the grout like wee and pour it in. Job done.

 

[Dune]

The idea of grout is that you get full bearing between the base plate and the foundation, not just relying on the packing shims. Anything bigger than 200mm square and a base plate should really have a hole for grouting. The grout should be runny enough to pour or inject to ensure no voids beneath the plate. This means some sort of former is going to be required around the edge of the plates.

Sorry but thats rubbish the bolts take the full force of the connection.

 

[stormin]

Sorry but thats rubbish the bolts take the full force of the connection.

 

[Pete.]

Sorry but thats rubbish the bolts take the full force of the connection.

You can't finish concrete well enough to give full bearing for a baseplate, it will only bear where it touches. Grouting gives full bearing below the plate for when it's under compression.

 

[Welderpaul]

Sorry but thats rubbish the bolts take the full force of the connection.

Why bother grouting then?!!!!!!!!!!

 

[Hitch]

Sorry but thats rubbish the bolts take the full force of the connection.

Not compessive loads surely?
If theres a gap under the BP the member will move easier regardless of how tight the bolts are?

In most instances the grout fills the gap between baseplate and pad, where its packed up to level...

 

[Welderpaul]

What about axial loads. When a column is side loaded, the outside edge of the baseplate wants to dip down - the grout prevents this, reduces flex, and presumably, reduces the loading on the bolts?

 

[Dune]

The grout is only used to make a seal between the base plate and pad, yes some loadings are imparted to the grout (as if you stuck your finger in there) but the connection should be designed to take all forces. These joints are designed only to take compressive and tension loads, if your imparting anything but small axial loads in any direction its been designed wrong. The bolts are designed to take all loads imparted into the base.

If we take a typical shape portal frame building and look at the loading diagram for one of the spans (frame would look like a kids house drawing). The centre of the member is bent out and the connections (base plates and joints) are in the original place. So you would have a loading of say 50kN at the extreme and 0kN at the base plate/hinge. Ill post a diagram to try and explain a bit further.

There are minimal side loadings from wind but the bolts are designed to take all the loadings and move a small amount to accept this. If the base plate is too secure it can cause failure of the members over a number of years.

 

[Pete.]

Bad news for all those buildings which have the column bases set in concrete.

 

[stormin]

Bad news for all those buildings which have the column bases set in concrete.

Not really. You don't see lots falling down do you.

 

[Dune]

Bad news for all those buildings which have the column bases set in concrete.

Plenty do, some are set in to the concrete and some of them are bolted and them cast in. They are designed differently.

And if you want to make smart comments do it with a bit of class.