Shear Wall Without Hold-downs

[helliot]

Hi all,

Does anyone have a good resource (and even better, Canadian?) for designing a shear wall without hold-downs at the end of wall segments?

i.e. if you are not providing concentrated anchorage against uplift at the ends of the wall, I believe you can design distributed anchorage instead (spread over the base of the wall). The concentrated anchorage load is based on a moment couple, but how does one calculate the distributed load on the base and design distributed reinforcement? For my application I would like to use nails.

Thanks for reading,

- h.e.

 

[jdgengineer]

I would imagine this is frowned upon as you would put the sole plate in cross grain bending. Why no holddowns?

 

[msquared48]

If you have enough dead load, you will not need holddowns.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[Cadair]

I've heard that the American Wood Council is working on a publication about this; however, they've been working on it for some time now, so who knows when it will be out. It can be done as it is done quite often with IRC walls. If you don't have deadload to take the place of the holddown and cross-grain bending is controlled, expect a significant reduction in strength for the first few panels.

 

[helliot]

FYI: The Canadian wood design manual states that hold-downs are not required if the following conditions are met:
1. Sum of factored basic shear resistance on both sides of the shear wall Vhd/Ls < 8.3 kN/m
2. Shear resistance of the wood based panel, vr, is based on nail diameter <=3.25mm and edge nail spacing >=100mm
3. Max height of shear wall 3.6m
4. Factored uplift restraint force at the bottom of the end stud of the shearwall segment Pj >=0

However, if you do not use hold-downs then you apply a factor Jhd to lower the shear resistance of the wall. The manual states that anchorage is still required to transfer uplift forces.

In my case, the dead load does not eliminate the overturning but the other conditions are met. So I don't need hold-downs connecting the wall to the sill plate to the floor below, but do need anchorage to transfer sill plate uplift to below. I was curious if this anchorage can be distributed in any way along the base, rather than say, a bolt or threaded rod near the end of the wall (as shown in the example in the code)

Based on your mention of the AWC, Cadair, I found this online:

http://www.awc.org/publications/Papers/WDFPLine.pdf

- they show that one would add distributed anchorage for a perforated shear wall base. This doesn't exactly apply to my situation, but I'll take a closer look at it and see what else I can glean from it.

Thanks,

- h.e.

 

[MiketheEngineer]

Sure - if you put about 100 tons of weight on it. Buy the damn bolts - they are relatively cheap!!

 

[OldPaperMaker]

Helliot,
Go to

http://www.apawood.org

or call their Product Support Help Deak at (253) 620-7400. They put out a technical bulletin about this subject in the last year or so.

I hpoe that this helps.