single angle joist seat
single angle joist seat
(OP)
I have a situation where there are joists framing into a concrete wall. Very standard situation. We would like to use an angle for the joist bearing seat that is welded to an embedded plate into the wall. What kind of design checks do I need to do on the joist seat? I know I need to make sure the weld is adequate and the headed studs in the wall are adequate. But what kind of checks do I need to do on the angle itself? I was looking in Chapter F of the specs in the steel manual, but I wasn't having much luck. Is there a check to make sure the horizontal leg of the angle doesn't buckle? However, according to Ch. F, the leg local buckling check only applies when the toe of the leg is in compression, which I don't have. Any help would be much appreciated. Thank you.






RE: single angle joist seat
RE: single angle joist seat
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6"
RE: single angle joist seat
1. You have a vertical load applied to the horizontal leg of the angle. This imposes a bending moment on the leg only, trying to bend the horizontal leg downward. Bending is about the leg's horizontal neutral axis...yes, fairly small Zx, Sx, and Ix.
2. Calculate the properties of the leg using the following "beam" properties: beam width b = horizontal angle length tributary to your load...for joist seats I'd use 6" to 12" at most. Beam depth d = angle leg thickness.
3. Calculate the bending moment on the leg. I would not use the wall to angle tip distance but rather I'd use half the angle leg width - in your case 6"/2 = 3". Even if the load is applied at the tip, the natural bending of the leg will move the applied reaction point closer to the wall. Moment is joist reaction R times 3".
4. Since the "beam" is bending about the weak axis, buckling is not a concern. Use the ASD or LRFD weak axis bending checks per the AISC Spec.
RE: single angle joist seat
I believe this is a logical interpretation of the code. What do others think? Is what I have done valid?
RE: single angle joist seat
That is exactly what I was getting at - Thanks!
RE: single angle joist seat
RE: single angle joist seat
RE: single angle joist seat
If the load of the joist (spaced at 6' o.c.) requires (3) anchors then you can't just space them at 2' o.c. You have to consider where the anchor is in relation to where the joist is. Is it spaced evenly between anchors? Is it located right on an anchor?
If you have on anchor located right at the joist then it will pick up all of the load.
RE: single angle joist seat
CODE
|<= b =>|
___________________________
\ /
30-45 deg \ ___ / 30-45 deg
.......\| |/..........
| x |
| | joist seat
________|___|_________
RE: single angle joist seat
Also use same philosophy to check bending at bolts.
csd
RE: single angle joist seat
DaveAtkins
RE: single angle joist seat
I highly recommend this book if you can find a copy...it's an excellent resource for anyone who is routinely designing with joists and deck