Pipe support on concrete slab, OK? 4

[MIEngr]

From a ignorant ME, I have a existing 8" concrete slab with 2 layers of 6x6 WWF 10 guage for rebar. My question is can I place a 9'-5" W6x15 Column to support 1-3" pipe assumed to be full of water? The slab is 50'x50' and I'm in the corner 15' off of each edge.

My concern in over turning forces and as a ME my initial response is to "red head" a pipe support into anything that has concrete.

 

[JedClampett]

I would advise against it. Any lateral loading due to wind, seismic or water with a 9'-5" moment arm will overstress the slab. Plus with that thin of a slab, the anchor capacities might be reduced. Also, slabs on grade are notoriously poorly built with varying thicknesses and wandering wire fabric.
If the loads above are negligible and this is a slab on grade, have them saw cut out a 3'-0" square, pour a 12 inch footing with anchors embedded in it and use that. If there are seismic, water pressure or wind loads, get a structural engineer to design the whole support.

 

[J1D]

MIEngr,
Get more info from the pipe stress person to determine maximum bending moment. Consider the slab as plain concrete. It might be okay if the column (free standing?) is to just support a 3" dia "cold" water pipe.

If the pipe support is outdoor, you need to conside wind on the column and on the pipe. Another thing usually critical is the slab movement (if frost heave or consolidation settlement presents), sometimes the movement excesses piping's tolerance.

 

[tincan]

What distances are you spanning between support points? The 3-inch pipe full of water doesn't weigh over 10-11 #/L.F. Unless you have more loading than this, you are not going to overload the slab(with an appropriate base plate).

 

[JedClampett]

When I read your post I misinterpreted the pipe size (One 3" pipe vs a 1'-3" pipe). However, my advice would be the same. Slabs on grade are typically shoddy structural members. Any kind of post-installed anchors are dependant on not only the installation of the anchor but the concrete. A new footing is very cheap.

 

[haynewp]

8" is a pretty thick slab, the footing may only be 4" thicker.

I really don't think enough information has been given to say whether it would work or not.

 

[MIEngr]

haynewp

What additional info do I need to be concerned with? I saw that JedClampett stated a 1' footing would the additonal 4" make that much a difference.

The support is outside and although I listed the line as full of water it is a relief valve discharge line so it is empty 99.9% of the time.

The existing slab also has 4 vessel foundations cut into it. Add it is 17' to the next pipe support on one end and 5' on the other.

Thanks for the help guys (and ladies, if applicable)

 

[haynewp]

I would want to know the span of the pipe between supports and what kind of seismic area. Also, I would ask for the base plate and proposed anchorage information. Condition/age and strength of concrete also.

I don't think anyone wants to tell you what you are asking is alright, and you get the impression just because the slab works means the base plate to slab connection itself is no big deal.

 

[JedClampett]

Yes, a 12 inch slab is only 4 inches more than a 8 inch slab. But that's 50% more thickness. Plus, the quality of a 3 ft. square footing is likely to be better than 8 inch flat slab construction. You can also cast anchors into a new footing.

 

[SlideRuleEra]

MIEngr - What you have described (and worse) is done all the time a electric generating stations. I have often been amazed how well some of these "solutions" work. Probably has to do with the robust design/construction of industrial facilities - very forgiving.
In my opinion, your proposal is reasonable for the conditions, even though, as others have pointed out, it is not optimal.