Compressive buckling on a plate intended for bracing.
Compressive buckling on a plate intended for bracing.
(OP)
Good morning all,
I was wondering you opinions in this subject. I have designed an eccentrically braced inverted U braced frame on a structure. The controlling factor means of failure was the KL/R of the whitemore section in compression. I had 50 kips of compressive force on my braces. The whitemore section is displayed in AISC Fig. 9-1. In order to reduce my L factor we welded 2 transverse stiffeners on the braced plate to the column and to the braced plate. I used the distance from the transverse stiffener to the top bolt as my L. Do you guys feel that this was an effective way to reduce my buckling factor, and have you ever seen this done?
I was wondering you opinions in this subject. I have designed an eccentrically braced inverted U braced frame on a structure. The controlling factor means of failure was the KL/R of the whitemore section in compression. I had 50 kips of compressive force on my braces. The whitemore section is displayed in AISC Fig. 9-1. In order to reduce my L factor we welded 2 transverse stiffeners on the braced plate to the column and to the braced plate. I used the distance from the transverse stiffener to the top bolt as my L. Do you guys feel that this was an effective way to reduce my buckling factor, and have you ever seen this done?






RE: Compressive buckling on a plate intended for bracing.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Compressive buckling on a plate intended for bracing.
RE: Compressive buckling on a plate intended for bracing.
RE: Compressive buckling on a plate intended for bracing.
1) Get that joint a lot more compact, starting with the work point modification that you mentioned and;
2) Consider a thicker gusset. It would look insane but, up to about 2" thickness, that would probably be cheaper than all of the stiffening.
You also didn't answer my question about seismic. If there needs to be a plastic hinge here, that changes things.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Compressive buckling on a plate intended for bracing.
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RE: Compressive buckling on a plate intended for bracing.
RE: Compressive buckling on a plate intended for bracing.
I couldn't say. Might be worth calling a local fab shop. Although, we've got some good fab guys here that may well chime in. What plate thickness have you been considering? While I stand by the 2" comment in principal, I was really hoping that it would be more like the difference between 1/2" and 3/4"-1". Might be kinda weird looking to gap your channels a full 2".
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Compressive buckling on a plate intended for bracing.
RE: Compressive buckling on a plate intended for bracing.
RE: Compressive buckling on a plate intended for bracing.
RE: Compressive buckling on a plate intended for bracing.
RE: Compressive buckling on a plate intended for bracing.
RE: Compressive buckling on a plate intended for bracing.
RE: Compressive buckling on a plate intended for bracing.
Pall = 19.8 x 0.625 x 6 = 74.25 kips
I laid out a geometry that the brace was 70 deg from the horizontal and the unbraced length of the gusset was 12" and I got lw=8.7", so I think the 6" I used is quite reasonable. So, like I said, I would really be surprised if the plate couldn't take 50 kips without stiffeners.
RE: Compressive buckling on a plate intended for bracing.
RE: Compressive buckling on a plate intended for bracing.
order of stiffeness:
base pl area of gusset
top portion of gusset @ col fla
web of col
I would expect more of the axial load in the gusset to migrate towards the free edge of the gusset pl and would check it's unsupported length as a precaution.....
RE: Compressive buckling on a plate intended for bracing.