Location of X-Bracing in warehouse 3

[CANeng11]

Due to architectural limitations (windows), we won't be able to locate cross bracing in the end walls of a new warehouse. Just wondering if there are any considerations of moving the bracing into the interior walls of the first bays on either side of the building? The building is 200 ft x 70 ft with 20 ft bays.

 

[BAretired]

Certainly!

BA

 

[Pmtottawa]

Torsionally brace to 1st interior bay

 

[Agent666]

I'd imagine for a 200 ft long building you might also require additional braced bays somewhere nearer the middle depending on how flexible your roof bracing is of course. Moving the end wall bracing in a bay of course cuts down the roof diaphragm span to 160ft which might help in this respect.

If architectural layout doesn't allow bracing one bay in (think about future use of the warehouse as well) then talk to architect about adjusting windows. Most warehouses are open plan so as not to limit use of the floorplate, so make sure architect and client are ok with any bracing located remotely from the building envelope. If bracing is in the way in the future it may just get removed (and not replaced), or will cost owner to relocate it. So I'd try hard to get it into the exterior walls for most practical approach to current and future flexibility of the space.

 

[MIStructE_IRE]

You could portalise the bays in the other direction instead of providing cross bracing. Win-win! You get your stability, architect gets his windows.

 

[jimstructures]

mas745,

I assume your building is 70' wide & 200' long with 20' bays. How tall are your sidewalls? If they are not too tall, say less than 20', why not make the endwall frame a rigid frame and eliminate the bracing in the endwall frame entirely. My experience is that the cost to make the endwall rigid is not a great deal higher than the endwall bracing, so it s a reasonable trade-off. If the building is a great deal taller than 20' than it does go up and might make the costs unacceptable. I am speaking about pre-engineered buildings here so if this is a conventional steel building I may be completely out to lunch in my suggestion.

Jim

 

[Ron247]

If this is a PEMB, the following are the more common methods of bracing a beam and post endwall in order of how common they are to encounter.

[ul]
[li]X-brace in the plane of the wall (what you say you cannot do)[/li]
[li]Rod bracing in the plane of the roof back to the first rigid frame as suggested by Pmtottawa. (the frame must be designed for the added lateral force)[/li]
[li]Rigid frame (design for half a bay) ( Suggested by jim)[/li]
[li]Rigid frame (design for full bay) ( used when you think you may add on in the future)[/li]
[li]Fixed-Based windpost ( 1 or more in the endwall)[/li]
[li]Shearwall from wall panels (rarely used and not generally desirable)[/li]
[/ul]

 

[BUGGAR]

Wherever you put the bracing will be the location of a door in the future.

 

[CANeng11]

For Pmtottawa's suggestion of torsionally bracing back to the first bay (new location of the vertical cross-bracing) would that be accomplished through horizontal cross-bracing in the roof of the first bay?

 

[KootK]

For Pmtottawa's suggestion of torsionally bracing back to the first bay (new location of the vertical cross-bracing) would that be accomplished through horizontal cross-bracing in the roof of the first bay?

It depends on what you have to work with. With decking as your diaphragm, you could probably just cantilever the diaphragm without discrete bracing. If the existing decking is not a structural diaphragm, then horizontal cross-bracing would probably be the way to go. You'd need to take a look at the roof diaphragm as a whole, including diaphragm chord elements, to come up with a well considered strategy.

HELP! I'd like your help with a thread that I was forced to move to the business issues section where it will surely be seen by next to nobody that matters to me:

http://www.eng-tips.com/viewthread.cfm?qid=456235