Precast Concrete Table-Top Machine Foundation

[humanengr]

I would like to ask if anyone has experience utilizing pre-cast concrete for a table-top structure supporting vibrating machine / compressor.
My concern has to do with the joints (Beam to Column, and Top Slab to Beams).
The joints will consist of grouted rebar sleeves. The grout is high strength, 14,000 psi (structure concrete strength is 6,000 psi).
The grouted sleeves will develop far in excess the strength of the rebar.
However, since these joints do not consist of contiguous concrete, I'm concerned there could be some unexpected modes of vibration.
Furthermore, the joints will have shear keys and a 2 in. gap between columns and beams which will be filled with the high strength grout.
I am still trying to find data to substantiate that the grout in the joint will not fail due to the vibrations (several million cycles per day albeit at
low stress levels).

If you have had experience with precast concrete structure(s) supporting vibrating equipment or if you have
any comments on the topic, your feedback would be appreciated.

 

[WARose]

As someone who has done a lot of vibrating equipment bases, my gut instincts are saying "no". (Without seeing more detail.) But if you have to go with it.....I'd get specific vendor info on the sleeves. (I.e. do they have any testing results of high cyclic loading?) If they don't have such info, I'm not sure I'd try it. Checking in ACI 215 (their fatigue code) I see no mention of this.

There probably is some data out there on high cycle loads with sleeves in some journal.....but you don't know if your vendor's sleeve will be like that sleeve. (Maybe compare the two?)

That being said, what kind of unbalanced forces are we talking here from this compressor? It's one thing if we are talking a couple hundred pounds.....and obviously something else if we are talking 100-300 kips.

 

[humanengr]

WARose, thanks for the response. I don't have actual machine data yet.
Centrifugal - 3,000 rpm, 40,000 HP Motor. Possibly 30~40 kips.

 

[WARose]

Yeah, with those kinds of loads.....you are going to need hard fatigue data. You may want to search for a vendor that does a lot of AASHTO work. Sometimes people use (types of) precast in bridge work.

[red]EDIT:[/red] As a alternative, you may want to change connection type(s). If you made it out of A36 steel.....and anchored with headed bolts......that is predictable (and data is readily available).

You may find something on sleeves......but just wanted to suggest this.