wood knee braced structure in SDC C

[MikeE55]

I am reviewing an old open structure, framed with wood posts and beams. There are no elements to provide lateral stability other than knee braces at the columns. Would this structure be permitted in ASCE 7, and what category would it fit in in Table 12-2-1? My SDC is C. I know this structure is grandfathered into the Code, but I would like to run calculations to see if there is a significant problem with either wind or seismic.

 

[msquared48]

Are you sure that this is not a pole structure? Sometimes even those have knee braces.

Mike McCann
MMC Engineering

 

[allcad1]

Hello all,

I use table 12-2-1-g-6 for timber structures.

minds_I

 

[MikeE55]

Thanks, allcad1. I had missed the reference to timber in 12-2-1-g-7. Mike, out of approximately 30 columns, only two of the columns go into the ground. The rest sit on a concrete gradebeam or on concrete piers with no visible means of attachment. Part of my scope in renovating this structure is to install some brackets to anchor each post to the concrete. It's a 100 year old building, so I want to treat it with respect and not add anything to hurt the character. However, when I get done with this, I intend for it to be good for uplift. I'm leaning toward adding 4 steel columns, cantilevered, but hidden in wood, to carry the lateral loads of the building. When I checked the knee-braced frames, they seem to have too much drift to be allowable (H/120 ?).