Steel Joist Sizing
Steel Joist Sizing
(OP)
I need a suggestion or recommendation on how to make a 8" deep steel joist fit in a 9" space.
The existing steel joist is supporting the metal decking and concrete topping on the second floor (e.g. joist supporting second floor), which is supported by a beam spanning in the opposite direction of the joist. It is flush-frame, and the depth of the existing joist is 9" (built in 1960's). However, we want to use an 8" or 10" deep joist... is there a way to fit an 8" deep joist into a 9" space? Or, is there a way to fit a 10" deep joist into a 9" space?
Any help would be appreciated. Thanks!
The existing steel joist is supporting the metal decking and concrete topping on the second floor (e.g. joist supporting second floor), which is supported by a beam spanning in the opposite direction of the joist. It is flush-frame, and the depth of the existing joist is 9" (built in 1960's). However, we want to use an 8" or 10" deep joist... is there a way to fit an 8" deep joist into a 9" space? Or, is there a way to fit a 10" deep joist into a 9" space?
Any help would be appreciated. Thanks!






RE: Steel Joist Sizing
Is the problem the accessibility of the bearing points at the ends of the joist? In other wor4ds, is it impossible to maneuver a joist of the same length into the same space?
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Steel Joist Sizing
Clarification is required; as it stands the answer appears trivial.
RE: Steel Joist Sizing
Dik
RE: Steel Joist Sizing
Why are you trying use an 8" or 10" deep joist. You could always spec a 9" joist and designate it as a 9 KSP and list the loads on the drawings.
RE: Steel Joist Sizing
RE: Steel Joist Sizing
RE: Steel Joist Sizing
Yes, I need to replace the 9" joist (severely corroded) with either an 8" or 10" joist, and I have to make it fit in that space. I've thought of using plywood under the 8" joist, but I don't think it'll meet the fire code.
We don't have 9" joists readily available here in Hawaii. It'll cost an arm and a leg to ship that size overseas.
Thanks!
RE: Steel Joist Sizing
If this does not work, you should provide a cross section to explain the space limitation. It is difficult to guess.
RE: Steel Joist Sizing
I guess the question was... what do I need to do in order to make the 8" joist fit into the 9" space so that it can be supported by the cross beam underneath? In order to fill the 1" gap, what do I need to do, e.g. use plywood, weld steel plates, etc. And if using 10" joist, do I cut the bottom web to make it fit?
Thanks.
RE: Steel Joist Sizing
RE: Steel Joist Sizing
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Steel Joist Sizing
RE: Steel Joist Sizing
RE: Steel Joist Sizing
RE: Steel Joist Sizing
http://www.vulcraft.com/
You stated previously that you live in Hawaii and that getting a 9" deep joist would be to expensive. How is it that you have 8" deep joists available? Usually steel joists are made to order.
I think what you are looking for is an 8" or 10" deep steel beam. Am I correct?
RE: Steel Joist Sizing
Are you thinking to partially remove and replace the deteriorated segment of joist, and that's reason why you worry about matching joist with different sizes? I don't think partial cut and replace is a good idea. You should replace the full length joist, or you may consider build-up beam segment fit to the cut-out with full pentration weld. Not easy, but can be done.
RE: Steel Joist Sizing
I believe you are talking about the truss joists.
What I'm looking at is provided by Dietrich Metal Framing, which has a manufacturing plant out here in Hawaii. In their SSMA catalog, they have joist sections which are called S-sections. They have 8" and 10" deep S-sections available, but not 9".
The existing steel joists (in the pic) are 19" o.c. and are hung off of the cross beams.
Thanks!
RE: Steel Joist Sizing
Yes, I will be replacing the full length of the joist.
So, are you saying that I should replace it with another beam or joist and full penetration weld the bottom flange onto the cross beam with a 1" steel plate?
Thank you!
RE: Steel Joist Sizing
Full pen-weld is required only if you are doing cut & fit a small segment of the joist. For full replacement, you may fillet weld the joist web (to the cross beam web) on one side, or both side, depends on the strength level required.
As the original 9" joist is hang off/weld on the larger (looks like 10") cross beam, your 8" replacement joist should fit into it without problem. There is no bearing plate required to fill the gap (2" from bottom of joist to bottom of cross beam).
Before you do anything, why not ask someone to review your cal to make sure everything would work out as planned. Good luck.
RE: Steel Joist Sizing
RE: Steel Joist Sizing
Also, if necessary, I think 10" joist might work too, but you may have to cope (cut out) the bottom flange at the ends to fit the joist into the cross beam (assume 10" too).
Again, check your cal. Hope everything work out smooth, good luck.