steel canopy possible issues
steel canopy possible issues
(OP)
Im dealing with a new steel canopy (above entrance of an existing building.) I want to talk about possible issues regarding this design.
Primary steel beam is H section (8 m in span).
Secundary beams are hollow/box profiles that are connected in the middle of primary beam (it has to be in the middle).
Since cantilever is 1,40 m long I suspect that there will be quite a torsion acting on a primary H beam, but this is solved by anchoring in existing structure on the other side of secondary beams (support reaction at the end shows upward). Is that correct?
Since its a cantilever, a connection of box profile to H profile should be fixed (moment) connection. Bolts will be in tension. Im wondering what road should I choose/you suggest:
Connection 1 or connection 2.
Im worried about 1 since cantilever is connected directly to the web of H section (but there is no need for additional plates that way).
tnx for help



Primary steel beam is H section (8 m in span).
Secundary beams are hollow/box profiles that are connected in the middle of primary beam (it has to be in the middle).
Since cantilever is 1,40 m long I suspect that there will be quite a torsion acting on a primary H beam, but this is solved by anchoring in existing structure on the other side of secondary beams (support reaction at the end shows upward). Is that correct?
Since its a cantilever, a connection of box profile to H profile should be fixed (moment) connection. Bolts will be in tension. Im wondering what road should I choose/you suggest:
Connection 1 or connection 2.
Im worried about 1 since cantilever is connected directly to the web of H section (but there is no need for additional plates that way).
tnx for help









RE: steel canopy possible issues
This is a load path I came up with...
cantilever causes rotation (torsion) of H beam. So the moment M is transfered through cantilever beam to bolts and from there to flanges of H beam. I have to prevent rotation of H beam so that means that top flange needs to be supported in my opinion. So the beam on the right is in tension... Is that right?
But what happened if we place this beam in the middle of H section (like cantilver beam in the right)? how do forces gets transfered?
I really need to prevent any rotation of H beam since any small rotation causes in large deflection at the end of catilever beam.
I also want to prevent any rotation because of the connection at the end of H beam (connection with column - weak axis).
RE: steel canopy possible issues
What is your loading? Is it wind only? Is there an additional live load on the canopy? Will it support people? What is the spacing of the HSS sections?
As for your connections, No. 2 will yield less deflection from beam rotation assuming the web of your wide flange beam is thinner than your flanges; however, it will require a different welding technique (overhead position) which is more difficult in the field. You could also consider a different type of connection that would include a gusset for the beam to help with resisting torsion.
Your framing system will also be more difficult to add roofing since your HSS outriggers are not at the same level as the top of the beam. Why is that?
RE: steel canopy possible issues
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: steel canopy possible issues
@Ron:
What is your loading?
self weight, wind and snow
Will it support people?
NO.
What is the spacing of the HSS sections?
0,90 m
RE: steel canopy possible issues
RE: steel canopy possible issues
If you can't weld the whole thing as an assembly in the shop and transport it to site, the connection 1 is best, provided the beam is deep enough for access for bolting.
RE: steel canopy possible issues
RE: steel canopy possible issues
Tough to argue with that logic. Another attractive way to do a canopy like this is to attached the hollow sections to the underside of the beam. Is this a glass canopy?
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: steel canopy possible issues
WARose,I fail to see a torsional concern. Significant twisting displacement in a closed section, a lot of stress. But in an open section, the same twisting displacement results in much less stress. Stress follows stiffness.
RE: steel canopy possible issues
Depends on the circumstances. But I've handled enough torsion problems to know that it doesn't take too much displacement to get some decent stresses in wide flanges. If someone is designing to the edge....it could put them over.
Granted, it's not the first thing that comes to mind that needs to be checked in this. (What Connection #1 will do to that web is the first thing that jumped out at me.) But the OP sounded like he thought this detail eliminated it.....so I just wanted to make that point.
RE: steel canopy possible issues
BA
RE: steel canopy possible issues
But I can't for the life of me see the difference between the end plate connection both sides and the pass through connection, except that the end plates would stiffen the web more.
RE: steel canopy possible issues
I don't know if the numbers would work out or not (you would probably have to consider a unbalanced snow load). But it's something to consider.
RE: steel canopy possible issues
RE: steel canopy possible issues
Dik
RE: steel canopy possible issues
The pass through connection has a cleaner appearance and eliminates localized bending of the end plates but otherwise has no particular advantage.
BA
RE: steel canopy possible issues
Well this is the only other option that investor agreed upon:
I think thats much better.
RE: steel canopy possible issues
RE: steel canopy possible issues
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.