Wood Perforated Shear Wall Design

[McQSE]

I posted an Excel program for wood perforated shear wall design over at exelcalcs (

http://www.excelcalcs.com/repository/strength/civil-engineering/orderby,2/page,3/).

Let me know if you try it and find something that does not work or other ways it may be improved.

 

[MiketheEngineer]

That "Page was not found" ??

 

[KBVT]

You may want to incorporate dead load from the wall tributary to counteract the applied lateral load. Using the correct load combinations, this could reduce your uplift requirements at your chords.

 

[bylar]

Pretty limited. Allow differet size panels and more than the 3 equal panels shown.

 

[McQSE]

KBVT-
Thanks for you suggestion.

bylar-
The size an number of panels is unlimited. The only input for panel size is the sum of panel lengths and there is not an input for the number. The image is only presented as an example of the application.

 

[NKT]

It seems that you haven't addressed the horizontal tension forces at the openings. The vertical chord forces as shown are normally not an issue since there is a continuous stud at the edge of each opening. Part of a perforated shearwall design is usually determining connections to transfer horizontal loads at the opening corners. The analysis for this is similar to a collector force calculation.

Also, it seems that you haven't addressed the shear in the panels above and below the openings (to transfer the holdown forces past the openings). The shear in these panels can be quite large if the opening is tall compared to the wall height.

I don't immediately see how you can address the above issues within the generalized format you've set out in your spreadsheet, as the calculations require specific opening sizes and panel lengths for each "collector" force calculation.

 

[McQSE]

NKT-
Framing and connections around openings are not required to be desinged for force transfer for the perforated shear wall design method. The shear wall capacity is reduced based on the size of the openings for a perforated shear wall. If you design for force transfer around openings, you get the full capacity of the wall. (IBC 2305.3.7)

 

[KBVT]

I agree with McQSE, force transfer calculations around openings are not required for the perforated shear wall design method.

 

[RVSWA]

I like it, clean presentation. It would be nice to add the loads of wall and other elements to calculate overturning.

Question how do you address the Anchorage Force for Uplift in the construction of the wall? Nail withdrawal or hardware? I have been trying to figure out how to balance the labor and materials involved in this provision. Anny advice or insight on this topic would be great.

 

[McQSE]

Thanks for your input.

It would be nice and fairly easy to add a distributed load on the wall. It may not be as straight forward as it seems though when you factor in all of the possible uplift forces. The gravity loads could be looked at to resist or counteract three types of uplift:

1. Uplift from roof bearing if there is any by the
time you get to the shear wall
2. Shear wall anchorage uplift between wall ends (t)
3. Shear wall anchorage uplift at wall ends (R)

I would start by using gravity forces to resist my roof uplift and then my uplift between walls (t) and then any remaining for wall end anchorage. I am not sure that the program would be the best place to figure this out. It is not a difficult calculation but it seems to me that there could be some confusion on whether the gravity loads have already been used to resist an uplift force or not. I welcome any further thoughts on this.

I have had the same struggles with trying to balance labor and materials for uplift anchorage. I tend to use hardware most often while keeping in mind some other modes of resistance (nails and sheathing lap). I like to use hardware because it makes it easier for me to verify the connection is there. As opposed to depending on nails that would be more difficult to check.

Take a look at this article from Structure Magazine (

http://www.structuremag.org/Archives/2006-3/C-SD-Enhanced-Lateral-Design-March-06.pdf).

I found it very useful.

Also, here is another document I found useful for this subject.

http://www.awc.org/Publications/papers/WDFPLine.pdf

I plan to include shear wall deflection calculations in the spreadsheet at some point.

 

[JMC3178]

I have been informed by my local city official and a representative from ICC that since the formulas for the perforated shearwall design in the IBC is empirical, that the dead load resistance from the roof (ect.) is to be ignored.

Anyone have thoughts otherwise?

 

[DaveAtkins]

I suggest you have your local official and the ICC representative talk to Ed Keith at the APA. He told me many years ago that it is legitimate to use dead load to reduce uplift at the hold downs.

DaveAtkins

 

[RVSWA]

...which makes absolute sense, I agree, otherwise what is the point in performing calculations. I am curious though if there is any report or data that JMC3178 can use to verify this... With the support of the ICC representative, the Local City Official is probably comfortable leaving their interpretation closed for discussion. I just reviewed McQUE's suggested reading to see if they included dead load contributions, neither example did, most likely it wasn't their intention to demonstrate their statics ability and distract from the main point. It is assumed they have these skills just like it is assumed that because dead load is present that it should be included after applying the appropriate factors.

 

[StructuralCA]

IBC 2305.3.7 is clear that uplift is to be calculated from load cases defined in Chapter 16. The overturning uplift in perforated wall defined in EQ 23-3 is only the E portion. The resistance moment (from DL) is to be included in the load case as usual.

You can also argue that you are following AF&PA SDPWS as an approved alternative to 2305 (Section 2305.1.) In that case APA opinion is what counts.


M.Genidy

 

[JMC3178]

Original question to John Henry, P.E. ICC:
Section 2305.3.8.2.4, Equation 23-3. Can net overturning moment (OM-RM) be used to calculate the uplift forces? The equation only uses OM and will give a very conservative result. Please clarify.

Response:
Perforated shear wall design in the IBC is an empirical method. The code refers to Section 2305.3.7 but explicitly requires a minimum uplift force T, given in equation 23-3. If the engineer doesn't agree with that then they should use the segmental shear wall method instead.
***************
Any thoughts? Any contact information for Ed Keith?

 

[smokiibear]

John...any chance you can email your excel program?

Thanks.