Wood and Steel Strap Columns
Wood and Steel Strap Columns
(OP)
Hello All,
I have this design problem: a roughly 20' tall 5-1/8 x 5-1/8 GL column supports a ridge beam. The GL column is undersized for buckling and needs to be braced or built up in the field. (The column sits in a wall with lots of windows and is supported in the plane of the wall at about 6' intervals. The out of plane direction is the problem.)
A coworker suggested using continuous Simpson steel straps on each side of the column, with the theory being that the straps are strong in tension. I am not comfortable with this solution and haven't been able to find anything on designing built up columns with steel straps.
Anyone have any thoughts or advice?
I have this design problem: a roughly 20' tall 5-1/8 x 5-1/8 GL column supports a ridge beam. The GL column is undersized for buckling and needs to be braced or built up in the field. (The column sits in a wall with lots of windows and is supported in the plane of the wall at about 6' intervals. The out of plane direction is the problem.)
A coworker suggested using continuous Simpson steel straps on each side of the column, with the theory being that the straps are strong in tension. I am not comfortable with this solution and haven't been able to find anything on designing built up columns with steel straps.
Anyone have any thoughts or advice?






RE: Wood and Steel Strap Columns
Can you install a knee brace from ridge to column?? Or add an interior sister column that looks "nice"?? Or use a 5 x10 (dimensions??) that looks "nice" Or do it anyway and cover with drywall.
RE: Wood and Steel Strap Columns
Instead of straps, what about 1/4" steel plates? They will actually provide some capacity that you can count on and calculate.
How close is the column to working? Can you beef up the properties or section a little to get it to work?
RE: Wood and Steel Strap Columns
Only two options are possible at this point since the column and windows are apparently in place:
1. Install either an interior or exterior knee brace (if the ridge beam extends far enough outside of the window wall) of sufficient length to satisfy the column instability. The Architect will love this one unless you can arrange some form of a hammerhead knee-brace detail. Might work actually. And...
2. Install another interior and/or exterior column to build up the section in the weak direction, thru-bolting to gain some composite action. The result may look massive Architecturally relative to the rest of the wall, but that's the result of the undersizing in the first place.
What are the lateral deflection ratios in the window wall system currently at the column?
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Wood and Steel Strap Columns
Or take it out and put in a HSS.
The other suggestions are fine, your problem sounds like it is architectural more than structural.
RE: Wood and Steel Strap Columns
RE: Wood and Steel Strap Columns
I should have mentioned that we were able to brace the column with horizontal beams at about the half way point, at a floor diaphragm level. The tall wall is two-story, so the beams will be exposed.
I was mainly curious about the straps, though.
Thank again.
RE: Wood and Steel Strap Columns
RE: Wood and Steel Strap Columns
Be careful about mixing wood and steel, especially reinforcing one side of a wood column with steel. Wood shrinks and grows with moisture content (to a lesser extent in the longitudinal direction) and an assmetrical reinforcement may be a curved column in a few years.