Knee Braced Frame Tube to Tube Connection

[marinaman]

I've got a steel frame where the beam to column connections are knee braced. There is approximately 22.5 kips in the knee brace members (6x6 diagonals at 1:1 slope). The diagonal knee brace centerlines intersect the column centerlines approximately 6' below the horizontal beam centerline.

I'm trying to determine the best diagonal brace to tube column connection.

I don't want to buckle or bend the face of tube steel column. For this reason, I'm shying away from placing a tab plate right down the center of the column face. I probably will not do that.

I'm trying to determine what my alternatives are.

I've considered welding a segment of WT to each face of column. The flange of the WT would span across the face of tube column so that I don't buckle the column face and then I could slot the diagonal to receive the WT stem. That's one alternative. If I do this, how would one check the parallel face of tube column to be sure it doesn't buckle?.....I'm thinking Euler......but then again, the edges of the face parallel to the load are braced and rigidly fastened.

I've also thought about a thru plate, but, this would require the fabricator to slot the column some 6' below its top to allow a plate to pass thru the column, and then, weld the pass-thru-plate to each column face it penetrates, all around....but again, this seems to want to locally bend the face of tube column.

Have you guys got experience with this detail......or know of a better detail?

 

[TehMightyEngineer]

Chapter K of the AISC is where you'll want to go. Also, AISC design guide 21.

The WT makes a lot of sense. Also, bolted end plate with blind bolts or perhaps field weld the HSS braces directly to the face of the HSS12x12.

Maine EIT, Civil/Structural.

 

[jike]

We would use end plates on the diagonal.