Steel joists at columns
Steel joists at columns
(OP)
I have a single story building with 44LH9 roof joists that span 69 feet to W18x40 girders. The girders span between 10 inch columns at 26 foot spacing between column lines. The building is resisting lateral loads by perimeter masonry shear walls. The joists are simple span. At the column lines, does the bottom chord of the joist need to straddle a stabilizer plate (not welded though). The stabilizer plate will be welded to the flange of the column.






RE: Steel joists at columns
RE: Steel joists at columns
I would bite the bullet and install a wide flange beam at the column in place of that one joist.
RE: Steel joists at columns
In answer to the first question - you do not have to extend the bottom chord to a stabilizer plate for LH joists when they occur at columns. You only need to supply a bolted connection. Stabilizer plates are required for joist girders, not joists.
Having said that, many engineers do provide an extension to the bottom chord and tie into columns for a some feel good, traditional reasons:
1. To provide some minimal lateral structural integrity of the overall building frame.
2. To provide for lateral restraint of the top of the column to restrict lateral buckling, or roll-over of the beam when the beam runs continuous over the top of the column.
RE: Steel joists at columns
You bring good points. However, if the engineer is going to use the joist or girder as part of moment frame to resist lateral loads, I think this should be indicated on the plans in addition to the axial for anticipated. This will afford the joist designer the opportunity to design the joist or girder properly.
Regards,
Lutfi
RE: Steel joists at columns
But for non-moment frames, there is no need to extend the bottom chords. Its just that a lot of engineers do to create a feel-good extra lateral stability.
RE: Steel joists at columns
I agree and I have my standard detail that calls for the stabilizer plate at columns for joist and joist girders.
I was lucky and won a book that was written by Dr. James Fisher and others tilted "Designing with Vulcraft steel joists, joist girders and steel deck"
I think it is an excellent addition to any SE library.
Regards,
Lutfi
RE: Steel joists at columns
If you use wide flange sections at column lines, you save the issue of worrying about keeping them supported until they're bridged.
I don't know how contractors are implementing these requirements. And if you put in wide flange shapes, I'm not sure the contractor will know the reason and put them in first.
RE: Steel joists at columns
Both are simple "pinned" supports and provide no substantial lateral bracing to the frame - that should be dealt with by other means such as cable tie-downs.
SJI/OSHA requires the joists on the column lines to be bolted connections (vs. welded) so the attachment can be made quickly and for the purpose of dis-allowing the joist bays to spread apart and allow intermediate joists to fall.
RE: Steel joists at columns
Since there is no OSHA requirement that wide flange members be supported until bridging is installed, you can fly them in to brace the column and then continue with the joist installation.
Are there any contractors out there that have dealt with this?
RE: Steel joists at columns
RE: Steel joists at columns
RE: Steel joists at columns
RE: Steel joists at columns
RE: Steel joists at columns
RE: Steel joists at columns
The joists I usually pick are based on at least 240plf uniform load on a 50ft or less span. By the economical joist guide, the best pick is a joist that does not require bridging before release anyway.
RE: Steel joists at columns
Here is a link to osha & joist
http:/
regards,
Mark
RE: Steel joists at columns
Mark
RE: Steel joists at columns
I think I stand corrected as this document appears to indicate that stabilizer plates are required. I'll have to look into this a bit more but I know there are lots of jobs out there that don't have them. I'll check with a local SJI joist supplier.
RE: Steel joists at columns
RE: Steel joists at columns
RE: Steel joists at columns
Mark