large force in double wood top plate 2

[kenna]

Does anyone know of any new methods being used for designing wood wall top plates for large chord and drag strut forces (in the range of 16K to 23K? I am trying to come up with a good solution and I am concerned with the amount of nails required and spacing of the nails. A 3x6 plate will transfer the force, but the nailing between two 3x's is excessive when you consider the diapragm and shear wall nailing going into the same member. We have considered several options including lag screws, bolts, and steel. Does anyone have a favorite method that the contractors are actually constructing correctly? I know we can add simpson straps but that does not completely solve the problem and that would also require quite a few nails.

Thanks!

 

[MiketheEngineer]

Those seem like very large forces.... Any way to break this structure into "boxes" that stand alone??

 

[jike]

I agree with Mike. You need to reduce this force by adding additional shear walls or other forms of bracing.

 

[RARWOOD]

How long are your drag struts and what is the shear load per foot?

 

[kenna]

Thank you all for your thoughts.

The building is 115' long and 63' deep with a plate height around 17 feet and 10 foot to 12 foot high parapets. A similar building has been done for our client by a couple different engineers, however, I believe the parapet heights were much lower and the wind code was different.

I believe it is the wind loads with the new ASCE7-02 and 05 on parapets that is creating the high forces. We cannot add another shear wall at midlength to my knowledge. We definitely need to fine tune our numbers. With even a 200 plf load to the diaphragm, the chord force for the long direction would be about 5.3 kips. The wind loads we are getting are in the 400 plf to 700 plf range. To help further the difficulty, we have a shortened shear wall length on one side of the building to 25.5 feet, where we have a similarily high dragstrut load.

I have some ideas for a solution, I just haven't found one that I like that much. Thank you again for your thoughts and posts.