Offset of drags to shear walls

[joengineering]

Hello,

What are some option if you have a building structure with no drags leading into the shear walls. The diaphragm is steel deck w/ no concrete.

Please see sketch to get an idea of what I am talking about.

So there is no direct load path to the shear wall since no drag beam placed. Any options??

 

[msquared48]

No picture...

Mike McCann, PE, SE (WA)

 

[joengineering]

I dont know what happened to my better sketch. I created this one, were the violet line represents the drag beam that should be there but is not. Red are beams or columns. So how can we transfer the load?

 

[KootK]

Sticking with traditional "shear panel" assumptions, you've got a bunch on nothin', which you've rightly identified. You could claim shear transfer over the length of the walls only if you can demonstrate that a n-s strip of deck as wide as the walls can resist in plane bending without the benefit of chords. If you do that, pay special attention to deflection and your sheet to sheet deck connections. I'm assuming deck runs N-S.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[manstrom]

Add diagonal struts?

When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.

-R. Buckminster Fuller

 

[slickdeals]

Do you need more than the length of the wall to transfer your shear? In other words, do you need drag struts?

 

[jike]

This looks like a very small building......can you rely on the outside walls for stability?

Somehow you either need drag struts directly aligned with shear walls or as manstrom said diagonal members with connections to force the offset drags to move together with the shear walls. Do you have shear walls in the other directions?

 

[joengineering]

jike..lets say I can't rely on them because they have many openings.

manstrom...see attached sketch here...so diagonal struts like the ones you see on this attachment in blue?

slickdeals....yes, I do not want to rely only on the exterior walls.

 

[KootK]

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[KootK]

Multiple ways to skin that cat.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[msquared48]

OP:

Are you absolutely sure that these interior walls are shear walls? Were they detailed as such with the reinforcing steel?

Mike McCann, PE, SE (WA)

 

[joengineering]

Yes I am sure.

 

[joengineering]

Kootk,
for the effective diaphragm. Where is the load transfer from the shear walls at the center? Wouldn't the force from the center drags create out of plane on the beams attached to it?

 

[KootK]

Where is the load transfer from the shear walls at the center?

I'm not quite sure what you're asking here. Does the sketch below help? Maybe I should have drawing the chords more "continuous" looking.

Wouldn't the force from the center drags create out of plane on the beams attached to it?

Yes. Itsy, bitsy weak axis bending moments. Technically, the same is true for the flanges of any continuous steel I-beam.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[joengineering]

That sketch and your responses clarify things. Thank you.

 

[wannabeSE]

Not much information is provided. For instance, why can't drag struts (collectors) be added? What is the shear force into each wall; how long are the walls. What is shear capacity of the deck. Is it correct to assume that the building is constructed? Is it occupied? Is the goal to remove some roofing and fix this from the top, or is it more desirable to fix from the bottom. Or, are the top and bottom of the deck accessible for remediation? Has a thorough analysis/investigation been performed to determine the drags are required?