Grouting steel column head plate to slab soffit (i.e. overhead grouting)

[Martin.H]

I have a steel fabricator who propose to grouting a steel column head plate to concrete soffit over.

My feeling is the only way to do this effectively would be to shutter 3 sides of the head plate and ram in a non-shrink grout mixed to a dry pack consistency.

My other feeling is the chance of this being done correctly is low!

Does anyone have real world experience of the success of such overhead grouting arrangements?

Martin.

 

[HTURKAK]

I would prefer shimming then grouting with ram in a dry pack non-shrink grout to all around.. what is the space ht.? You may post a sketch to get better responds..

 

[Martin.H]

Thanks HTURKAK, I agree shimming also, but I suspect that will also obstruct the grout and ramming.

Martin.

 

[Enable]

It's done quite often. Though I don't really trust most people to do it correctly without appropriate supervision. I've personally done the grouting and if I didn't care it would be very easy to say fuck it let me just make the outside look pretty. It's actually a rather tedious and tiresome process!

But again it's done often and I haven't heard of a failure yet so...but whatever you do make sure you specify a large gap. Larger gaps are easier to shove material all the way to the back. When engineers get cute and spec less than 2" it is basically just asking for laborers to give up getting the drypack to the back.

CWB (W47.1) Div 1 Fabricator
Temporary Works Design

https://www.enable-inc.com/

 

[KootK]

I'm in favor of dry pack grout as well. My intuition tells me that the analogous condition in column base plates would also show considerable defects if one were able to look inside. But, then, life & engineering must go on...

It might be advantageous to use a slightly expansive grout mix for an application. Your core concern with this, after all, is probably just a somewhat uniform distribution of the slab load into the steel column without thing getting hung up on any unintended hard spots.

 

[bones206]

I’ve never had an issue with drypack grouting in this type of application.

That being said, I think it might be adequate in this application to omit the grout and bring the column cap snug to the soffit through careful anchor bolt adjustment. The cap has such a small bearing area that I doubt flatness variability in the soffit would be an issue.

One other thought would be to provide bearing pad material similar to what’s used for precast bearing just for more assurance of even load distribution.

Just to reiterate my overall point, since you have vertical adjustment capability at the baseplate, I don’t think you really need another load transfer mechanism (i.e. drypacking) at the top of the column.

 

[KootK]

I do like the precast bearing pad concept, particularly if there are a number of these situations such that a small batch could be ordered.

 

[Martin.H]

Thanks all for the replies, very useful to get a range of views.

Martin.

 

[bones206]

When I posted my reply I had pictured in my mind a stand-alone post, like a slab prop of some sort. However if the column is supporting other framing besides the slab, then most likely the anchor bolts cannot be used in the way I proposed. The anchor bolt adjustability would be needed to set the framing TOS elevation and therefore would not be available to adjust the column cap elevation.