Tube to Tube Connection 1

[marinaman]

I have an unusual detail where I have a HSS 16x8 vertical member sitting on top of a 16x4x1/2 horizontal member.

The load in the vertical member is small, at only 27 Kips max.

I am trying to be sure I'm comfortable with the vertical sitting on top of the horizontal. I don't think its likely that the 16 x 4 walls would buckle, given the short 4" dimension, wall thickness, and the continuous 16x4 member, but I am unsure how I could check that numerically if I wanted to.

The horizontal member is 20' long. There is only one 16 x 8 sitting on top of the 16 x 4, and that's at the mid-length of the 16x4. The 16x4 is continuously supported by the W21x93, and, has a W16 x 26 at the centerline of the 16x8/16x4 to aid in supporting the 16x8 and to prohibit the 16x4 from rotating.

I'm I over thinking this....and am concerned over the 4" tall wall for nothing.....given the small load?

Thanks for everybody's input.

 

[jdgengineer]

AISC 360 Chapter K has the provisions to check HSS for concentrated loads taking into account.

 

[marinaman]

jdgengineer,

As best I can determine, Chapter K does not address this situation.

 

[TehMightyEngineer]

If I recall correctly it does, see K2.2b of the 2005 AISC 360.

Maine EIT, Civil/Structural.

 

[jdgengineer]

That's one heck of a memory

 

[TehMightyEngineer]

I only glanced at the section to find the number but didn't check 100% it's applicability but I recalled using it for a similar connection a few years back.

Maine EIT, Civil/Structural.

 

[Structcon]

Both walls are 1/2" and 4" is less than 8" for oop buckling of the wall, therefore ok by inspection.

 

[Bagman2524]

AISC 360 section K2.2b is used to check chord plastification and shear yielding (punching). It's not used to check for buckling of the walls. Table B4.1 gives the limiting width to thickness ratios. Case 12 is for HSS members in uniform compression. The limiting b/t is 1.12 SQRT (E/Fy) = 1.12 SQRT(29,000/42) = 29.4.
The actual b/t is 4/0.5 = 8; 8 < 25 OK. Appendix K of the 9th edition deals with determining if web stiffeners are needed and how to size them.

Faith is taking the first step even when you can't see the whole staircase. -MLK

 

[glass99]

Could you not do a simple Euler buckling check? I just did a rough number based on a 4" long column 4" wide and 0.5" thick. The buckling capacity per wall is 745kip, so 1490kip total.

 

[Bagman2524]

Glass99's approach seems reasonable. I believe AISC Table B4.1 width/thickness ratios are based on Euler buckling

Faith is taking the first step even when you can't see the whole staircase. -MLK