PIN or FIX support?
PIN or FIX support?
(OP)


These are the lay out of the supports. Its an I beam that support a platform and it was connected to a concrete structure. can i assume this support as a PIN support at major axis and FIX support at minor axis so i can reduce the stress on the bolt and at the same time to reduce the LE consideration for LTB check? Can i assume that its a PIN support as long as the bolt is inside the section's Flange. Or can i consider it a FIX support as long as it can resist the moment reaction even though the lay out of the bolt is inside the section's flange? All opinions are very much welcome. thank you in advanced






RE: PIN or FIX support?
RE: PIN or FIX support?
depends on the rotation ....
best regards
Klaus
RE: PIN or FIX support?
the most conservative approach would be "overlapping assumptions" ... pick pinned when analyzing the beams (as this should cause the highest stresses in the beam), pick fixed when analyzing the ends (the welds, fasteners, and local structure).
another day in paradise, or is paradise one day closer ?
RE: PIN or FIX support?
For lateral torsional buckling:
- I would certainly consider the joint torsionally restrained.
- I would not consider the joint torsionally fixed as that requires a degree of weak axis (flange strong axis) joint stiffness that is difficult to guarantee.
Overlapping, as rb1957 said.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: PIN or FIX support?
Whenever I am in doubt about something like this I'll run it both ways and be sure the detail can handle the reactions for either one.
RE: PIN or FIX support?
RE: PIN or FIX support?
I'm afraid that this is an unfortunate myth. If anything, this arrangement exacerbates tension in the bolts and the forces that tax the connection plate by reducing the lever arm over which the inevitable moment acts.
One alternative:
- bolt a loose plate to the concrete.
- weld a standard AISC double angle connection to the loose plate.
- SSL or LSL holes for errection tolerance.
This may not jive with your corrosion protection strategy, however, as field welding would require touch up work on the galvanizing.
Another alternative:
- support the beam on a seat angle bolted to the concrete.
- install a bolted web angle with LSL holes to prevent roll over.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: PIN or FIX support?
RE: PIN or FIX support?
RE: PIN or FIX support?
@motorcity this is the framing plan
RE: PIN or FIX support?
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: PIN or FIX support?
RE: PIN or FIX support?
RE: PIN or FIX support?
A loose plate anchored to the wall is really easy to fabricate. Horizontal slots in the plate allow some tolerance for anchor placement. The contractor can choose to weld the shear tab in the field or in the shop.
The same connection on the other end is really simple.
The anchors to the concrete are designed for the shear from the beam along with the moment created from the bolts being eccentric from the concrete by a few inches.
RE: PIN or FIX support?
RE: PIN or FIX support?