twin beams combined torsion
twin beams combined torsion
(OP)
I have a disagreement with a local authority checking engineer concerning torsional restraint for interconnected beams and would welcome other views.
The side/side two beams 8 meter length(305/165 UB & 305/127 UB)carry the two skins of a domestic cavity wall and are intended to be interconnected at 1.5metre centers by means of bolts/spacers at the center of the web and with 100mm wide steel plates (welded or bolted) to the full width of top flanges at the same positions. My design assumes effective length for the beam of 1.5 meters and my feeling is that the beams will restraint each other against torsional bucking. The checking engineer's view is that the twin beams could buckle "as one". Is this possible, is this realistic, or it just an oversafe consideration?
The side/side two beams 8 meter length(305/165 UB & 305/127 UB)carry the two skins of a domestic cavity wall and are intended to be interconnected at 1.5metre centers by means of bolts/spacers at the center of the web and with 100mm wide steel plates (welded or bolted) to the full width of top flanges at the same positions. My design assumes effective length for the beam of 1.5 meters and my feeling is that the beams will restraint each other against torsional bucking. The checking engineer's view is that the twin beams could buckle "as one". Is this possible, is this realistic, or it just an oversafe consideration?






RE: twin beams combined torsion
RE: twin beams combined torsion
RE: twin beams combined torsion
think about the case when both are loaded with large loads, when beam-1 wants to buckle-out then Beam-2 will "brace" Beam-1 by taking lateral load, if Beam-2 doesn't have sufficient capacity to resist the lateral load and since it is also loaded... this lateral load will induce buckling in beam 2 as well. now Beam 1 and Beam 2 want to sway out and there goes the system.
Basically you do not have anything bracing the system except the composite weak axis section properties... which the bar isn't doing anything substantial.
Or that is how I would look at it...
RE: twin beams combined torsion
RE: twin beams combined torsion
RE: twin beams combined torsion
RE: twin beams combined torsion
RE: twin beams combined torsion
I think that you should lose the top plate altogether. What you need here is vertical shear transfer between beams. The tubes will get that done and the top plates will make little difference.
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: twin beams combined torsion
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: twin beams combined torsion
If you do this again, I'd recommend omitting the tube spacers and adding a few extra bolts as I've shown in the lower portion of the sketch.
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: twin beams combined torsion
RE: twin beams combined torsion
If space allowed the installation of bolts, I'd really like to have stiffener plates in each beam that overlap in the space between in a bolted connection. Wishlist.
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: twin beams combined torsion
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.