4 Story Building w/ Metal Deck on Wood Frame 14

[cap4000]

Has anyone ever designed concrete on metal decks bearing on wood frame construction. The architect seems to think its OK?? Any tips will be greatly appreciated. Thanks.

 

[ztengguy]

As long as its designed for the load, whats it matter what the support is? A column designed to hold 1000 lbs will do it as good as a column designed to hold 1000 lbs. Note I left out the materials.

 

[cap4000]

The building code is silent on this combination.

 

[msquared48]

There have been other discussions on the subject here.

I do not like to do it. but if it needs to be, I would consider a glulam beam that you couls camber for the dead load of the concrete.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[cap4000]

These are load bearing wood walls supporting 4 concrete metal deck floors

 

[ztengguy]

What is the load at the lowest level? What would the walls need to be to support? If the design, servicability, and code works, why the issue? If you cant get a design to work, then there is your out.

As a structural engineer we are to take the loads, review the code, design the members, and then report that its ok, If its not ok, then suggest a different material to the Arch.

 

[cap4000]

Only in the talking phase. Architect is trying to have high ceilings with no joists. Deck would span wall to wall.

 

[BAretired]

Precast hollow core slabs supported on wood framing are commonly used in some Canadian cities for three and four story apartments. I don't care for it and have not seen it used in my area but it seems to be quite popular in Winnipeg, Manitoba.

BA

 

[SteelPE]

So the arch wants to use wood bearing walls with steel decking and concrete to act as a floor?

I understand your situation. It's something you haven't necessarily seen before so you don't know if there is some obscure part of the code that prohibits this form of construction. To tell you the truth... I don't know if there is. Please inform us if you find something.

Something you might be concerned with...... how is the construction process going to go? In a normal platform construction you would construct your walls, floor joists, decking and then begin the process again until you reached the top. In this instance you would have to construct the walls, put down the decking, pour concrete, wait for it to harden and then start over again. It almost appears as if you have multiple trades (I'm not sure the wood guys would do the decking and pour the concrete). Seems like a great way to slow the construction process.

local bending of the top plates may be a concern as well. Normally the joists line up with the studs eliminating plate bending..... you may have to check that here.

Good luck.

 

[nac521]

IBC 2009 2304.12 - refers to NDS for long-term load deflection issues

 

[XR250]

There will be a lot of weight falling down on the firemen when the thing catches fire.

 

[jwilki]

Down under we have white ants (protective measures are more like prevention, one can never guarantee), so it is a no no to have masonry let alone concrete floors supported on timber stud walls... fire would also ensure a swift collapse.

 

[MJB315]

Does it make any sense to use load bearing light gage metal stud walls instead of wood? That may help some long-term creep issues and just "feels better."

"We shape our buildings, thereafter they shape us." -WSC

 

[RFreund]

I hear a lot of 'don't like it' which I can understand. I guess my question (with out trying to hijack the thread) is why?
I see fire issue and slow construction but say the beams/posts met/surpassed the fire requirements, are there other concerns?

EIT

http://www.HowToEngineer.com

 

[nac521]

Why!? Because at the lowest level you will end up with a 2X6 @ 3" o.c bearing walls! There is a reason why its called 'light framed construction', because its light! A metal deck/slab will need to be around 9" for an assumed 20 foot span. A 14” wood truss or a 12” Hambro composite joist on metal stud load bearing are much better options for that span. Its not worth the extra cost (foundations, seismic lateral, shoring) to increase the DL by 100 PSF for 3”-5” of extra ceiling height. Additionally, now you have space in the joists or trusses to run MEP.

 

[msquared48]

In part, because wood tends to creep, crush, rot, and deflect under heavy weight, which concrete transmits, and concrete does not do well with deflecting supports, causing a lot more cracking in the concrete, and allowing penetration of water to deteriorate the wood support for the concrete.

Kind of a can of worms you might say...

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[focuseng]

Biggest issues I can think of is
1) make sure you check bearing.
2) Limit thermal bridging to prevent condensation
3) use P.T. wood in contact with the floor deck.

I think the code is usually clear that any wood in contact with concrete or masonry need to be P.T. Note that sometimes a P.T. wood plate is bigger than it's cousin, the non treated stud because it is still wet or is stored outside. This sometimes causes issues...

______________
MAP

 

[steellion]

Use wood framing with wood floors, or LB-metal studs will work with your concrete-on-deck floor.

 

[RFreund]

Makes sense, thanks guys!

EIT

http://www.HowToEngineer.com

 

[wadavis]

Some municipalities do not allow wood construction over a certain height / number of stories. Give your local building inspector a phone call.