Wood structural panel return

[jmpeter1]

I am in the process of designing a braced wall using the continuously sheathed braced wall method. The code states (R602.10.4.4; North Carolina Building Code) that there must be a 24" minimum wood structural panel corner return provided at both ends of a braced wall line I.A.W. Figures R602.10.3.3(1) and R602.10.3.3(2). It also states that you may use a hold down device with a minimum uplift design value of 800 pounds in lieu of the return. Now for my question... I have a customer who will be using gypsum board on the exterior to achieve the required fire rating. I am currently calling out (1)DTT2Z in lieu of the corner return because the code does not specifically state if gypsum can be used in place of the structural panels. I would like to save the customer money by not requiring the hold down if it isn't needed... does anyone have any insight into this. Secondly, what advantage are we actually achieving by using a 2ft return on the corners? I do not understand the need for the return nor can I find any explanation for it. Thanks for any info on this topic.

Jeff

 

[focuseng]

First of all note that using the "braced" wall provisions that you are in the PRESCRIPTIVE code and are not really in the world of being able to truly deal with an engineering analysis on a rational level. If you are using prescriptive methods then you much USE prescriptive methods and not mix it up. If GWB panels are not specified for your application then they are not on the menu.

If you can justify using a GWB panel to have 800 lb tie down then use it. Design the tie down of a GWB panel to the floor for 800 lb. I don't think you will be able to do this. however, in the realm of saving cost, a 800 lb tiedown strap is not that expensive. If you are on a wood floor deck then Try an LSTA18 from simpson, a bunch of 10d nails and you are good. The tie down is to the floor -not the foundation. Maybe in NC the floor is the foundation? Try a strap w/ masonry screws or nails. Not hard to do and simple compared to engineering the GWB.

The 2 ft return or the 800 lb tie down is the result you get in a pseudo-perforated shear wall in the gymnastic math of a one size fits all prescriptive design for any and all wood framed structures with-out regard for what it really looks like, and don't forget the old adage - "we've been doing this for years and never had a problem" argument. The Prescriptive code process is much like watching your state or the US congress come up with laws. Very political. In short it passed with the most votes.

MAP

 

[FSS]

If you are using the continuous sheathed wall bracing, then you can't mix in gypsum along the same braced wall line. You can mix in regular wood structural panels, just not continuous sheathing and the associated reduced lengths.