interior shear wall

[rittz]

We are designing a wood frame storage building 200 ft long 64 ft long 16 ft ceiling. There is a 22 ft door in each end. The available shear wall length is thus 42 ft at each end. My numbers give me a required shear wall resistance of over 700 plf at each end. One possibility to reduce the shear load at the ends could be by adding a shear wall inside. However that interior shear wall would have to bear more than half he lateral resistance. And that does seem too make much sense

Any comments would be appreciated.. Thanks
A sketch is attached.
J

 

[jdgengineer]

Personally, I'd want the interior shearwall just from a redundancy perspective if its possible. You meet the NDS aspect ratios for either blocked or unblocked but I suspect your diaphragm stresses and chord forces are probably very high. I'd also pay attention to your diaphragm deflection.

With the interior shearwall you could also check the requirements of a rigid diaphragm to see if you qualify. It's unlikely, but would allow a more favorable distribution of stresses.

If the interior shearwall really doesn't make sense, 700 plf isn't unmanageable by any means. [tt][/tt]

 

[briancpotter]

From a cost perspective, adding a wall and foundation is probably going to be far more expensive than designing the current walls/diaphragm to resist the load. I'd also guess that the owner wouldn't be thrilled about the reduction in storage space.

I don't see any particular problem with designing for 700 plf. Is the roof framing wood trusses/wood sheathing diaphragm? Has joist girders with light-gauge decking been investigated. In my (limited) experience, that's the more typical option for a roof this size.

Brian C Potter, PE
Simple Supports - The history and practice of structural engineering.
ConstructionPic - Send annotated jobsite photos.

 

[Archie264]

rittz,

Out of curiosity, how is the frame constructed? Is it heavy timber construction or something else? I'm simply asking to learn, as, in general, buildings of this approximate size, shape, and use have always piqued my interest. Thanks.

 

[BAretired]

Without an interior shear wall, the roof diaphragm has a length to width ratio of 3.125 which is a bit too limber for my liking. Perhaps horizontal truss bracing in the plane of the ceiling should be considered.

The shear in the end walls would be close to the limit for a wood-based panel on S-P-F framing. The factored shear resistance for a 15.5mm panel with 3" nails (3.66mm dia.) at 50mm centers is 15.3 kN/m or about 1050#/' or a working load of 700#/'.



BA

 

[Triangled]

I've seen wood diaphragms with double this shear, but I agree with the above that the building is limber and diaphragm deflections and chord connections will be the challenge.

 

[Triangled]

oops, I meant horizontal wood diaphragms in above post.

 

[rittz]

Thanks guys

Archie, This building certainly piqued my interest too. Never did a building this long before. It’s long and high and wide open.

You fellows may have more to see when you check the quick sketch attached.

Thanks for the responses.

J

 

[Archie264]

Thanks for the additional info. So it looks like the stud walls are anchored into the concrete knee wall? Is it bolted in using a bottom plate and anchor rods? If so I'm trying to resolve in my mind what keeps it from a folding failure mechanism. I guess the shear walls, which brings us back to your original question. Am I interpreting it correctly?

 

[rittz]

Archie ... Yes the Stud walls have a bottom plate which is bolted to the concrete wall.The concrete wall
is connected to the piles at 10 or 25 ft intervals. (pile spacing)

 

[rittz]

The Owners have added a full-length lean-to to each side as shown on the attached sketch. By fire code issues the entire front and 2 ends cannot be walled in. There would now be an opportunity to create a braced frame to supplement the shortage of shear wall length. Does this idea have any merit anyone?

 

[msquared48]

1500#/ft should be no problem with one layer of 5/8" CDX each side of the wall. The hold downs would be of concern though to me. And, rather than the braced frame, I would span over the top of the 10 foot wall the 16 foot full length of the wall to lower the size of the hold downs needed for the 5' shear walls.

Mike McCann
MMC Engineering

 

[rittz]

Thanks so much Mike I like that idea The frames are a pain ...cost and looks.

John

 

[msquared48]

FYI, I meant to span over the 10 foot wall OPENING, not the 10 foot wall.

My hands are not as fast as my brain, or is it the other way around?

Mike McCann
MMC Engineering