Do composite metal decks upset MRI machines?

[demayeng]

Has anyone done a suspended slab under an MRI with composite metal formwork?

Thanks

 

[271828]

Yes, this is done. See the AISC Design Guide 11 Chapter 6. The generic vibration limit is extremely tight, however, and you might find it almost impossible to satisfy.

I'd recommend to get the vibration limit from the MRI manufacturer and have a vibration consultant predict whether or not the design will be OK. The limit will be in terms of either a regular narrowband spectrum or a broader-band spectrum such as in one-third octaves, so it will probably be tough to deal with from a typical SE's perspective. However, it can be done. I've done this myself for multiple jobs. Usually, it's a matter of bumping up the sizes, but to extremely large ones required to satisfy Ch. 6.

You could contact the AISC Steel Solutions Center. They might give a list of people who do this sort of thing.

 

[hawkaz]

The project physicist will need to confirm your specifics. I have had projects where the metal deck was not an issue, and others where it was. In those cases, they used copper lined flooring to accommodate.

In every case, they had a physicist determine the appropriateness.

 

[SteveGregory]

How about reinforcing in the slab? Should they use fiberglass rebar?

 

[frv]

That's two things I had never heard of in this thread: "Project Physicist" and Fiberglass rebar.

 

[SteveGregory]

Check out

http://www.fiberglassrebar.com/why_composites.htm

 

[TXStructural]

The issue of reinforcing steel in slabs is a red herring for most imaging applications, but some owners believe it to cause problems. If the machine supplier requires non-magnetic reinforcement for whatever reason, I would follow the manufacturer's spec.

If you have to remove magnetic steel from the slab, your options include any of the 300-series stainless steel reinforcing bars or mesh. This allows you to stay consistent with your design strategy.

 

[demayeng]

Thanks all

The MRI guys say that they can handle normal ferrous reo as long as it is in a regular pattern, however we've decided to go with precast floor panels and will probably use 304 stainless anyway as the quantity won't be that great to be prohibitively expensive

 

[a2mfk]

I've done several MRI jobs, and the MRI manufacturer always gives me very exact specs that give amounts/types of steel and the minimum distance required. Sounds like you are in touch with them and on the right path.