Cracked blocks under steel column

[Hilldes]

So the timber frame is now up. We have a number off steel columns that rest on the perimeter foundation blockwork - e.g. goal posts over bifolds and we also have portal frames supporting glazed gables. The timber frame erectors have bolted the vertical steels onto the foundation blockwork. In some cases the blocks receiving the bolts have visible cracks and in one case (see pic) the block has split.

 

I'd very much appreciate thoughts on how to remedy.

 

Timber frame company have said this does happen from time to time and they will ask erectors to apply a "structural grout". The timber frame erectors have said they would normally expect padstones to be used in foundation blockwork below steels.

 

The column in the pic should support a load of almost 30kN (which I believe is about 3 tons).

 

P.S. got BCO inspection tomorrow.

 

[Conor]

The steels should be resting on high density padstones or pre stressed heads cut to size, not ordinary blocks. I can't tell from the photos what kind of blocks they are. Also, it would be better to use resined in bolts rather than expansion bolts. Either way, they need to be redone.

[Hilldes]

9 minutes ago, Conor said:

The steels should be resting on high density padstones or pre stressed heads cut to size, not ordinary blocks. I can't tell from the photos what kind of blocks they are. Also, it would be better to use resined in bolts rather than expansion bolts. Either way, they need to be redone.

 

Many thanks @Conor - the timber frame company had said they would use resined bolts before the build when I mentioned the frame would be sitting on blockwork and not reinforced concrete. The timber frame company actually supplied the expanding bolts instead to the erectors and the erectors used them without question.

 

The blocks you see on the top course are 140mm(wide)x440mm(long)x100mm(high). I will look up the compressive strength, but they are a minimum of 7N/mm2. Assuming the flange at the base of the steel is 150mm x 140mm x7N/mm2, that should support 147kN - so should be sufficient for the loading???

Edited March 30, 2021 by Hilldes
typo

[Mr Punter]

You will need to support the column from elsewhere and either fit RC padstones or cast them in situ concrete.

 

Normally need to grout the column base as well.

 

The expansion fixings are not suitable.

[Hilldes]

15 minutes ago, Mr Punter said:

You will need to support the column from elsewhere and either fit RC padstones or cast them in situ concrete.

 

Thanks @Mr Punter (and @Conor) to identify the padstones required, would I need an SE to calculate or is there a rule of thumb? A padstone like this (Jewson 440x140x100 which is "is designed to ensure exceptional load bearing capabilities")?

 

@Mr Punter Could you clarify please what you mean by support the column from elsewhere - you mean the padstone will need to extend more left and right in the photo than the flange of the steel?

Edited March 30, 2021 by Hilldes

[epsilonGreedy]

I am by no means an expert but does anyone else think the mortar below the cracked block looks a bit sandy i.e. more like a 5 in 1 mix. Would 3 in 1 be recommended? 

[PeterW]

36 minutes ago, Hilldes said:

 

Thanks @Mr Punter (and @Conor) to identify the padstones required, would I need an SE to calculate or is there a rule of thumb? A padstone like this (Jewson 440x140x100 which is "is designed to ensure exceptional load bearing capabilities")?

 

@Mr Punter Could you clarify please what you mean by support the column from elsewhere - you mean the padstone will need to extend more left and right in the photo than the flange of the steel?

Correct - that’s the padstone you should be using. 
 

You’ll need to jack up the frame to get the old one out, clean up the mortar beds and reset the new padstone. Then when it’s gone off (you can use rapid set but be careful) you will need to drill and bond the studs, wedge the base so it’s perfectly square and then pour or inject structural grout into the gap between the flange and the padstone. 

[TonyT]

When pouring grout, pour from one corner to get less air bubbles in the final mix.

 

resin would be better for holes that close to the edge..

[Hilldes]

2 hours ago, epsilonGreedy said:

I am by no means an expert but does anyone else think the mortar below the cracked block looks a bit sandy i.e. more like a 5 in 1 mix. Would 3 in 1 be recommended? 

It does look like that from the photo although I did specify 1 to 3 or 1 to 4....

[TonyT]

The mix should be a bit drier mix than normal, fully filled to the rear of the block 

[Hilldes]

2 hours ago, PeterW said:

Correct - that’s the padstone you should be using. 

thanks @PeterW will order the padstones.
 

So the resin fills the holes for the bolts and the grout fills any gaps between flange and pad stone. @PeterW @TonyT please could you recommend products to use?

[TonyT]

You resin in screwed rod, ( not the fixing you have already used) and tighten down with a nut and washer.

you can pack under the steel with 

https://packersandshims.com/product/pre-galvanised-square-horseshoe-packers-shims/?attribute_pa_dimensions=50mm-x-50mm-x-1mm-x-m12&gclid=EAIaIQobChMI9OPgx-fY7wIVmrp3Ch3_owf1EAQYBCABEgKDS_D_BwE

that will let you tighten down immediately and then fill the void with grout.

 

 

[Hilldes]

17 minutes ago, TonyT said:

You resin in screwed rod, ( not the fixing you have already used) and tighten down with a nut and washer.

you can pack under the steel with 

https://packersandshims.com/product/pre-galvanised-square-horseshoe-packers-shims/?attribute_pa_dimensions=50mm-x-50mm-x-1mm-x-m12&gclid=EAIaIQobChMI9OPgx-fY7wIVmrp3Ch3_owf1EAQYBCABEgKDS_D_BwE

that will let you tighten down immediately and then fill the void with grout.

 

 

Thanks, I know the bolts that go in the resin will not be the expanding type the framers used. What products please for the resin and structural grout - have not used these before 

[epsilonGreedy]

27 minutes ago, Hilldes said:

So the resin fills the holes for the bolts and the grout fills any gaps between flange and pad stone. @PeterW @TonyT please could you recommend products to use?

 

 

Here is an example of steel support columns being resin bolted to concrete foundations for a domestic extension.

 

 

[LA3222]

11 hours ago, Hilldes said:

Thanks, I know the bolts that go in the resin will not be the expanding type the framers used. What products please for the resin and structural grout - have not used these before 

When my goalposts were put up some hilti resin was used and I did the grout myself with sikagrout 111.

 

I've got one of the resin packs knocking about the house, I can take a pic tomorrow if that helps. 

 

The sikagrout was a doddle to use, I mixed in big bucket with drill and paddle mixer, not too much and then literally pouted it in. It flows really well. 

[Hilldes]

38 minutes ago, epsilonGreedy said:

 

Here is an example of steel support columns being resin bolted to concrete foundations for a domestic extension.

 

 

Spot on thanks! Btw it must have been really balls aching to cut those recesses in the footing concrete - really pleased I don’t need to do that.

[Hilldes]

39 minutes ago, LA3222 said:

When my goalposts were put up some hilti resin was used and I did the grout myself with sikagrout 111.

 

I've got one of the resin packs knocking about the house, I can take a pic tomorrow if that helps. 

 

The sikageout was a doddle to use, I mixed in big bucket with drill and paddle mixer, not too much and then literally pouted it in. It flows really well. 

Thanks will look for some sikagrout 111 and have the resin product from the video.

[Hilldes]

On the list of things to buy - the threaded rods - just normal or stainless steel?

[PeterW]

Normal bolts will do. They won’t rust in the resin and they are stronger. Fischer resin is really good - you need to get a blower though to clean the holes out and wear eye protection as you will blow dust into your eyes...