Steel Beam Cast in Slab on Grade
Steel Beam Cast in Slab on Grade
(OP)
I have a client (contractor)whose building clien wants to cast 6" steel beams into a 6" reinforced concrete slab-on-grade. They want to weld loops/hooks/etc. to the steel beams and use them as an anchor when using come-alongs to straighten bent/racked trailer frames. There will be one beam parallel to each side of a repair bay, ten bays total, thus 20 beams.
I suggested welding rebar to the flange of the beam to tie to the rebar mat in the slab. Am I being too conservative?
Has anyone done something like this? What magnitude of forces do you design for?
Contractor is obviously concerned that the slab will sustain excessive cracking etc and client will come back on them.
I suggested welding rebar to the flange of the beam to tie to the rebar mat in the slab. Am I being too conservative?
Has anyone done something like this? What magnitude of forces do you design for?
Contractor is obviously concerned that the slab will sustain excessive cracking etc and client will come back on them.






RE: Steel Beam Cast in Slab on Grade
In industrial plants steel beams are frequently embedded in concrete floors, without special anchorage, to serve as support for electrical switch gear and other components that are welded to them.
Also, a historical use of embedded steel beams was grillage foundations, which perform nicely, even under very heavy loads.
www.SlideRuleEra.net
RE: Steel Beam Cast in Slab on Grade
Do we need to take any extra precautions with the slab? I have it reinforced with #4 @ 24" o.c. each way.
RE: Steel Beam Cast in Slab on Grade
About grillage foundation, go to my website and download the 1923 Carnegie Pocket Companion, see page 252.
www.SlideRuleEra.net
RE: Steel Beam Cast in Slab on Grade
I would have two concerns about the situation you describe. First, it sounds like the steel beam would be in direct contact with the ground since it is 6" and is embedded in a 6" slab. There are ways to deal with this, but should be a consideration. Second, I would be concerned with concrete spalling where the steel beam is in contact with the concrete at the slab surface. I'm not sure what shape you're using but its been my experience that people can come up with some pretty unusual ways of twisting and pulling on things to get them back into place as you describe above. You may want to consider some sort of system that is independant of the slab (i.e. a stand alone foundation).
RE: Steel Beam Cast in Slab on Grade
I appreciate all the help I have received on Eng-tips; differing opinions and varied experiences spur us all to think and grow in our professions. Too often I have found seasoned engineers reluctant to share their knowledge. It's a sad and frustrating situation.
RE: Steel Beam Cast in Slab on Grade
I have those same concerns, as does the contractor. If we weren't talking about (20)- W6 30' long beams embedded in the slab, I would suggest a separate foundation system for them.$$$$
I think this will come down to "educating" the building owner about the potential risks associated with their scheme and getting them to sign off on it if they wish to pursue it.
RE: Steel Beam Cast in Slab on Grade
RE: Steel Beam Cast in Slab on Grade
www.SlideRuleEra.net
RE: Steel Beam Cast in Slab on Grade
If Tee sections not available, use back to back angles.
Frame straightening requires vertical and lateral loads, but the magnitudes are probably within a 10-20 kip range, since a come-along is being used.
RE: Steel Beam Cast in Slab on Grade
1. Is it possible to use other smaller sections, (check this with some calaculations). Consider the Tee section and Equal Angles back to back or a smaller section of Tee.
2. Base on the assumed loads to be calculated do you think increasing the depth of slab by 2" will upset the client, otherwise consider doing this. Corrosion becomes a big issue to tackle when it set in in a corbonated environment.
Aileme
RE: Steel Beam Cast in Slab on Grade
To guard against corrosion I would use a 600mm wide thickening at each beam, with a minimum of 75mm concrete below the beam and a layer of welded wire mesh within the thickening.
RE: Steel Beam Cast in Slab on Grade
Drive a beam vertically into the ground. A 10' W6 driven 9'+ into good soil and allowed to set up can take a great deal of load in any direction.
Advantages: it won't crack the concrete if an expansion joint is left around it, chains and come-a-longs can be easily connected to it without welding (some pre-drilled holes), it may be cheaper because you could have less total beam length, despite the cost of driving them.
Disadvantages: it will be a discrete system - you won't have a continuous surface to work from, if he requires many points to pull from this option will be more expensive.
One other note: you may be able to sell them on a mixture of the two, say half of the bays have continuous beams and the other have the driven stubs. What will happen is he will favor one or the other and gravitate to that side of the shop for any straightening work and do other maintenance in the other bays.
RE: Steel Beam Cast in Slab on Grade
They are going to pour "cow pies" to set the ends of the beams, so the beam won't be in direct contact with grade. Holes will be drilled at 24" o.c. so the rebar can be threaded thru.
I appreciate all of your insights into the design dilemma. I'm sure it will come in handy again.