Shear walls desing at corners in wood w/ plywood sheathing

[ammf]

We have updated to a higher wind load of 110 mph. We are also having to comply with sstd 10-99. This however creates a problem with the corners of our buildings such as at our garage doors where we can not have the required to be sheathed corners of 27" for one story and 32" for two story. It also creates a problem for window openings to close to the corners. I need a calculation or resolve to this problem so we can have less of our corners full hieght sheathed.

 

[ishvaaag]

Then you will have to prove that your structure doesn't rely at all in sheating there.

Maybe using lateral stability available in the main house, or use frame design at your conflictive points or planes is the solution.

Of course if what your code says is that once you rely somewhere on sheating for lateral stability you need to comply with such constructive restrictions some qurrelling with the reviewing party may or not be worth, since such party might interprete that the specifications need be implemented as a whole. Other interpretation wouold be that "if you need to use the entire wall, end panels can't be less than of such width". But if you don't use -nor you need to use- the entire wall?

 

[ammf]

The code says we have to use shear walls. The building department will not determine the wind direction and has told us that all walls will be shear walls to cover all wind directions. The code says that corners must be full hieght sheathed with 27" for one-story and 32" for two-story. We are trying to reduce this width to the corner and need to prove it's strength to be equal or better than the codes. I know I can put double layers of plywood, increase nail size, add straps etc. I just do not know how to show the calcluations to prove the strength. Is there a simple calculation to do this.

 

[ishvaaag]

Don't fail to see my comment for this in the roof question.

One thing is to use shear walls for stability and other that the whole length of the outer walls be required to be counted to satisfy the lateral stability requirement. Then you could argue that you are not using the corners for stability. You would be using the rest.

Now, with or without corners counting in a sehar wall, how is the strength determined? Normally where you build a code will be being enforced to this purpose, and normally it is there where particular precisions about what the strength of a shear wall is will be being made, to the aceptability of the design by the reviewong party.

Other than that, there are different ways of checking shear walls. Using a book on wood framing can do it. A common but not general assumption is that only the full height portions of the walls stand shear, teh collaboration through the portions with openings being in such cases dismissed.

Particular constructive details, such anchors to soil or sleepers also affect if feasibel to account.

In any case, if the approach is to investigate the full panel strengths, this uses to come tabulated both in the books and codes.

However the understanding of what the loads are and its distribution to wall or roof elements requires at least basic knowledge of statics, and for some codes more than that. If some of you is able to ascertain what the loads acting in a shear panel it, a look to one of the above named tables can give you the proof of that the particular solution of nails plus panels is going to satisfy the demanded strength.

The UBC 94 code had such tables, such Table 23-I-J-1.
UBC 97 must have (I practicing in Spain have not it).

Other beautiful reference with shear strength tables is

Wood Engineering and Construction Handbook 2nd edition
Keith F. Faherty
Thomas G. Williamson
Mc Graw Hill
Table 8.7

If the reviewing party becomes nosy with every time asking a calculation you are not able to perform, hire someone, will be simpler. If this is a problem that has easy solution under present practices, he/she will understand that just getting proof form say look to such and such tables (photocopy to you) will be enough and that's ok.

But of course, for more complex things, wood framing and cosntruction ia an entire technology, and it is natural to require the safety be warranted in reliable manner.

 

[inspectorjeff]

Use a drag strut (girder truss) across the front main wall over to the garage side wall.This will dump alot of the shear into the front wall and not the garage returns. then take 1/2 of the depth of the garage bump out from the house distance and calculate the lateral wind load on that area.
Now if the garage returns do not meet the 3.5/1 ratio of height to width you will need to either design the diaphragm in rotation or use fixed columns, or a cantilevered frame. Contact a P.E. for a typical detail.This is too involved for most.

 

[boo1]

Some other considerations to use are Strong-Wall Shearwalls, solid studs or sheathing both sides of the wall. These will increase the shear resistance of the corners and allow decreasing the wall lenght. Professional Engineering or AR stamp is required when devating