Steel Beam Embedded in Mat Foundation

[waytsh]

I have been asked to designed a small mat foundation for a laser cutter feeder rack. The manufacturer had a recommended detail which incorporated an embeded steel beam into a thickened portion on either side of the mat. This allows them to make the attachemnt to the foundation easier. The details which they have provided happen to be for a unit that is 20 kips lighter than the one I am working on which has a total weight of 120 kips. Thier details show a series of various sized stirrups placed around the beam. Can anyone recommend a good approach for considering the hybrid beam and mat design? I would assume that the full depth of the slab can be considered for shear since the top flange of the beam is going to be flush with the top of the mat and concrete will completely fill the space between the flanges. I was then planning to consider only the portion remaining below the beam for bending perpendicular to the beam. Do this sound reasonable?

I appreciate any thoughts.

Thanks

 

[dbuzz]

Isn't the embedded steel beam for connection of the equipment to the foundation rather than for reinforcing the foundation?

An alternative is to reinforce the mat foundation as normal and have a length of flat plate (say 100x12PL), flush with the foundation surface, with 'tangs' to anchor it into the concrete.

 

[waytsh]

I was told by a non-engineer that it was for making the connection to the foundation but I am sure that the original design was also using it to distribute the puching shear from the columns that sit on it.

 

[ChipB]

waytsh,
If you are going to do it as they have suggested, you are going to need holes drilled in the flange to allow the air to escape, minimizing the voids in the concrete. Typically, I do it as dbuzz has suggested and use Nelson Studs on the plate. Different plate size as well, but same idea. Usually you are just providing a surface for them to weld their equipment on.

Also, if it has any dynamic loading, make sure you have enough mass of concrete to dampen it. Typically, this is 3x the weight of the equipment.
Chip

 

[waytsh]

Thank you both for the input. I normally use the studded plate as well but was wondering if there was not some benefit to the emdedded beam which I was not aware of. There was another pad on the previous design which actually has more load and used the anchored plate instead of this beam. So they apparently had a reason for specifying it which makes me a little reluctant to take it out. Do you see any other pros or cons in additon to the consolidation of the concrete under the flanges?

 

[ChipB]

Depends on how long a member we are taking about. Might be easier to get a stiff beam properly located instead of a (possibly) wet noodle. Also could be due to their allowed tolerance in elevation. The plate might be more wavy. If their tolerance in elevation fluctuations is low, it would be easier to use the beam. I'm thinking as it is laser equipment, they aren't going to be able to tolerate much.