Stiffeners in Large HSS Columns
Stiffeners in Large HSS Columns
(OP)
I have a custom HSS section that is approximately 5' x 10", it is being used to support large overhead doors.
My question is, the section needs to be stiffened at the top where the pulley assembly mounts to the column. How do I determine how far the stiffeners should run below the mounting bracket.
I'm worried about creating a point where the stiffness changes drastically and creates a "soft spot" in the column.
The load the stiffeners are holding is about 1/8 of the wind load (Which acts in the strong direction of the column and opposite to the dead load of the door).
So if the stiffeners run to far down the column I would have the same problem from the wind force which is much greater.
any input would be greatly appreciated.
My question is, the section needs to be stiffened at the top where the pulley assembly mounts to the column. How do I determine how far the stiffeners should run below the mounting bracket.
I'm worried about creating a point where the stiffness changes drastically and creates a "soft spot" in the column.
The load the stiffeners are holding is about 1/8 of the wind load (Which acts in the strong direction of the column and opposite to the dead load of the door).
So if the stiffeners run to far down the column I would have the same problem from the wind force which is much greater.
any input would be greatly appreciated.






RE: Stiffeners in Large HSS Columns
BA
RE: Stiffeners in Large HSS Columns
This sounds like a basic stiffened seat design from the AISC manual but I'll reserve judgment until we get some more info.
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Stiffeners in Large HSS Columns
The initial wasn't a mistake, the modifications are required to an existing section as the pulleys and sheaves being mounted are changing location.
Also I am working with the Canadian steel code, if the AISC covers the topic better I would greatly appreciate some input in a direction to look.
Thanks
RE: Stiffeners in Large HSS Columns
Are you using the stiffeners to bring down the b/t ratio on the wide face of the column? If so, they'd need to run the full length of the column.
The localized stiffening doesn't bother me any.
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Stiffeners in Large HSS Columns
RE: Stiffeners in Large HSS Columns
Out of curiosity, how are you dealing with the b/t issue? I've got that at 152 for the wide face. S16 table 4-2 limits you something around 38 depending on your steel grade. I did something similar for a free standing canopy once. We had to weld angle stiffeners to the inside of the wide faces to keep b/t from getting out of hand. Maybe since the column is existing, it's already stiffened.
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Stiffeners in Large HSS Columns
Faith is taking the first step even when you can't see the whole staircase. -MLK
RE: Stiffeners in Large HSS Columns
BA
RE: Stiffeners in Large HSS Columns
basically if your b/t ratio is larger then the limits provided then you have either have a class 3 or 4 section. So for a Beam-Column analysis you can turn the section into an equivalent size that fits within the limit.
So take the b/t ratio, back solve for "b" then calculate your section strength with this property, realizing that that portion of the section is only able to fully develop without localized failures.
so specifically for the calculation that 5' long wall in theory became something like 1'-4".
RE: Stiffeners in Large HSS Columns
RE: Stiffeners in Large HSS Columns
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Stiffeners in Large HSS Columns
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Stiffeners in Large HSS Columns
Welding continuous stiffener plates inside an existing hollow section is not possible, but it may be possible to attach the two five foot wide plates together at discrete points from the exterior in order to provide some stiffening.
BA
RE: Stiffeners in Large HSS Columns
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Stiffeners in Large HSS Columns
I would ,if possible, close off the top of the col with a flat pl and put cutouts in it if reg'd. For the bottom fla of the quasi-top bm I would add a horiz external stiff if it is not possible to add one on the inside. With a top bm of depth up to 10" , it may be possible to get a weld rod in the...10x10" opening clearance.
Rather than do all that fab, the other possibility is to weld a ,say HSS10x10 to the top of the col , close off the ends with a pl that extends dn the ends of the col a certain length or extend the ends of the col up to use as a closure pl for the HSS10x10. Then detail a brkt conn to this top bm. I always try to close off the ends of HSS members...open ends on HSS members , not good. Ofcourse, none of this may be applicable as the info supplied is not complete.
RE: Stiffeners in Large HSS Columns
BA