What is an MPC 16 x 5 3/4 x 22 on a roof framing plan?

[Engineerataltitude]

We are working on checking the feasibility of retrofiting some heavy items onto the roof of a fairly large building in Southern CA. Building was built in 1979 and we have the structural plans. The roof framing plan calls out structural members none of us have heard of before. Plans are hand drawn, and the handwriting is kind of hard to read, so the members are either MPC 16 x 5 3/4 x 22 or MFC 16 x 5 3/4 x 22. The framing is a grid with what look like purlins at 8' oc and one big main center beam. All the same. Anyone have any idea what these are?

 

[JedClampett]

Sound a little like glulam. Are they wood?

 

[Engineerataltitude]

No idea. Haven't done any intrusive investigation yet. Still trying to glean what we can without tearing into the building.

We thought glulam was a possibility too, but can't figure out what all the numbers would be. 16 and 5 3/4 could make sense despite being non-standard today, but the last number is definitely not a length number. Maybe a grading designation?

Details imply that they may be structural steel.

 

[MiketheEngineer]

If it is wood - it could be 16'' deep by 5 3/4 wide??

 

[msquared48]

The "MPC" probably means "Metal Plate Connected". Are these open web trusses?

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[Engineerataltitude]

True. Although I never heard of wood or glulam beams being called out that way. What do you think the MPC would mean then?

The best I could come up with is that sometimes wood trusses are called metal plate connected (MPC) wood trusses. Still can't figure out what all numbers would mean if that were the case though.

 

[msquared48]

Could the metal plates be 16 gage, 5.75" X 22" long?

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[dik]

16 or 5-3/4 are not common glulam dimensions... depth usually multiples of 1-1/2" or 3/4" and width a tad less than the standard actual dimensioned lumber depth...

MPC... multiple ply construction? Do you have a photo?

Dik

 

[Engineerataltitude]

No photos. We haven't done anything intrusive yet.

We just picked up on the fact that there are some W section structural steel moment frames called out on a couple of the grid lines. Could it be that MFC means Moment Frame Compatible with the corresponding numbers being the envelope of dimensions the strucutral member needs to fit within to frame into the moment frames? Perhaps this technique would be used if the roof framing plan is handed off to a steel detailer who might size the intermediary framing members to be something cost effective or readily available. The framing members wouldn't have to be that strong, roof live load is only 20 psf with a max span of 32'. I've never seen that before, but it is a plausible explanation.

 

[Engineerataltitude]

If it would help...here is a scan of the roof framing plan. Sorry, not very good quality.

 

[msquared48]

With steel deck over, could it be a steel joist/girder system?

Enough guessing - visit the site and take some pictures!

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[hokie66]

I think they must be steel. There is a note on the drawing requiring weld washers on the steel deck, and that wouldn't make sense with wood members.

 

[JAE]

Metal Purlin Channel?

 

[Engineerataltitude]

Thanks everyone for your thoughts. Does look like we are going to have to open it up to see what is there. At least I don't feel so bad now that I didn't know what these were. If all you ETF folks with your collective experience don't know what it is either, I don't feel so bad.

 

[hokie66]

You have the roof framing plan. Don't you have the other drawings which should show the members in section?

 

[Engineerataltitude]

Just got a copy of another structural sheet, S11. I'll upload it. Am trying to scrounge up S12 & S13 and more particularly, the structural note set. That really may be where they spell out what an MPC is.

On detail 1 it shows the connection between the W-Bm moment frame and what looks like a W-Bm purlin that is one of the roof framing members that is called out on the plan sheet as an MPC member. Detail 2 also shows a side view of what looks like a W-BM, but is labeled an MPC12.

What the heck is that??