Sheathing to Decrease unbraced length

[tolind]

Howdy all,
I have a church that is wood constructioon with a couple of load bearing walls that I need to reduce the unbraced length in. These walls are going to have a layer of sheating on one side and I and trying to find a source that explains the allowable decrease in unbraced length. Can anyone shoot me in the right direction?

Thanks in advance for any and all help

 

[DaveAtkins]

The 1997 NDS, Appendix A, Section A.11.3, states that studs braced on one side are braced.

DaveAtkins

 

[tolind]

Let me explain it another way. Currently I have a exterior wall that is 14 ft tall. With the wind load on this wall section I need to increase the size to 2X8 instead of the 2X6 in all other locations. Now I add a layer of sheathing to the outside. I understand that the sheathing will reduce the unbraced length, allowing for a smaller member in this area. My questions is where can I find some information to verify the amount I can decrease the unbraced length. Sorry but I have not had a chance to check out 1997 NDS so I don't know if that is my solution.

 

[UcfSE]

Sheathing will only brace the compression flange for wind in one direction, not both. Since wind is reversible you should consider that in your bracing calculations/assumptions. The 2001 NDS in section 4.4 gives circumstances for when sheathing will reduce the unbraced length so that CL=1.0. Bascially it depends on the depth to breadth ratio and if the compression flange is continuously braced which you won't have. Otherwise maybe you can add more solid blocking with a good connection to the studs and sheathing to reduce the unbraced length. Remember that unbraced length isn't the length you use to find CL, you use Le from Table 3.3.3 of the 1991 or 2001 NDS. Check App A.11.3 to see how that helps you also by changing whether you use Le/b or Le/d.

 

[boo1]

Dont forget the internal pressure coef

 

[ronster]

Typically a 2x6 bearing wall should be able to span 14' (braced in the weak direction). What is controlling the design that forces you to go to 2x8's...axial load, bending moment from wind, or deflection? Is there any unusual loadings on the wall?