Steel beam end plate connections
Steel beam end plate connections
(OP)
I am wondering about the design of standard steel end plate and cleat connections for simple construction. I understand that the connections are designed to allow rotation of the beam ends and this principally happens by flexing of the end plates at the top of the connection between bolts. Hence the use of thin plates and large cross centres between bolts on the end plates.
All the design guidance I have seen refers to examples with pure shear for beams and then examples with pure tension for vertical bracing systems. However in most structures many of the beams are also part of the vertical wind bracing system and so they also have axial forces. Would the flexibility in these connections under axial loads render them inappropriate for taking significant axial forces. If so what can you do short of creating a fully fixed connection?
All the design guidance I have seen refers to examples with pure shear for beams and then examples with pure tension for vertical bracing systems. However in most structures many of the beams are also part of the vertical wind bracing system and so they also have axial forces. Would the flexibility in these connections under axial loads render them inappropriate for taking significant axial forces. If so what can you do short of creating a fully fixed connection?






RE: Steel beam end plate connections
RE: Steel beam end plate connections
RE: Steel beam end plate connections
RE: Steel beam end plate connections
ht
You see how the wind shears from the top level have to travel through the beam end connections at the mid level to go across to the next bay.
RE: Steel beam end plate connections
RE: Steel beam end plate connections
Even with those horizontal trusses where they span across two bays you end up with beams needing to take tensions through their end connections. Surely this is not such an uncommon occurrence.
The only guidance I found was in a book on connection design that said that the bracing cleats where they fix to the column and beam should not have unduly large flanges as they tend to restrict end rotation. They then show pictures of extended beam end plates which extend above and below the flanges with bolts all the way up and down. That seems like you would really end up with a fixed end connection for your beam.
RE: Steel beam end plate connections
DaveAtkins
RE: Steel beam end plate connections
I have seen a quite old factory building where a custom bracket was used: Picture a semi-circular block that fit into a C-shaped socket. Axial load yes, but free to rotate, and as such quite litterally a "pin". It was in drawings, but was apparently built in Boston in the late 1890s.
Weird how problems can just stick around; Then again it is a physical reality to be faced, so I guess the laws haven't changed with time. ;0)
Cheers,
YS
Cheers,
YS
B.Eng (Carleton), P.Eng (Ontario), MIPENZ (Structural-New Zealand)
Working in Canada, and missing my adoptive New Zealand family... at least I brought the little Kiwi with me!
RE: Steel beam end plate connections
I think Dave's response about double angles is appropriate. But if the forces are small then a single shear tab is good for some tension force along with shear. Maybe my confusion is in the end plate connection that you describe, but wouldn't you have tension and shear in the bolts, along with some prying action?
RE: Steel beam end plate connections
Perhaps there is a disconnect between the theory that the plate flexes, providing slight rotation, but it is not enough to concern me.
RE: Steel beam end plate connections
RE: Steel beam end plate connections
If the transverse load is small compared to the axial then I have typically designed it based on the axial loads since the rotation requirement is small.
I always try and get the bolts toward mid height of the beam to minimise rotational restraint.