Staically Indeterminate Trusses
Staically Indeterminate Trusses
(OP)
Hello:
I am a BSME in need of some Structural Engineering help. I am looking to engineer an awning truss system, accounting for snow load and possibly wind load (required?). The truss has a basic right triangle perimeter, and is supported along the wall side (short side) by three fasteners (all equally spaced). The end of the truss (furthest point away from the wall) on the bottom side (long side) is supported by a column. I wanted to add a snow load to the top side (hypotenuse).
With external forces being generated from a snow load (known), a possible wind load (known), a dead load (known), a reaction at the column (unknown), and 6 (3 fasteners x 2 directions each = 6) reactions at the fasteners, I end up with statically indeterminate equations after summing moments and forces.
Can anyone tell me how to proceed? Can I derive statically determinate equations from this setup? If not, how would this truss be analyzed? Thanks all in advance for your help.
I am a BSME in need of some Structural Engineering help. I am looking to engineer an awning truss system, accounting for snow load and possibly wind load (required?). The truss has a basic right triangle perimeter, and is supported along the wall side (short side) by three fasteners (all equally spaced). The end of the truss (furthest point away from the wall) on the bottom side (long side) is supported by a column. I wanted to add a snow load to the top side (hypotenuse).
With external forces being generated from a snow load (known), a possible wind load (known), a dead load (known), a reaction at the column (unknown), and 6 (3 fasteners x 2 directions each = 6) reactions at the fasteners, I end up with statically indeterminate equations after summing moments and forces.
Can anyone tell me how to proceed? Can I derive statically determinate equations from this setup? If not, how would this truss be analyzed? Thanks all in advance for your help.





RE: Staically Indeterminate Trusses
Get some software to help you out. Much faster and probably more accurate - if you model it correctly..
You could possibly simplify and assume only two reations - the post and the connections. Then split the connection load up over the three fasteners. Be conservative with the fasteners and you should be OK. I have often used this method and it seems work just fine - and actaully is not far off what the software says.
RE: Staically Indeterminate Trusses
You might want to consider moving one of the attachments against the wall so that you only have 2 reactions and the frame may not be statically indeterminate.
Dik
RE: Staically Indeterminate Trusses
for uniform load on one span only it will be roughly 50% to each of the 2 supports under the load, a little more to the central one.
There may be other issues such as bracing of the bottom chord that only a structural engineer would pick up so I would advise you to spend a bit of money on one.
RE: Staically Indeterminate Trusses
Once you are done with this, then you can figure out the vertical force where it is attached to the wall. Then you just just design the 3 clips to hold that load.
My theory is, if you get rid constaints to make it "determinate" structure, you are designing it more conservatively. (Because you brace it more when you build it). So just use one fastener when you design it.
RE: Staically Indeterminate Trusses
Dik
RE: Staically Indeterminate Trusses