Truss analysis loads to consider concurrent
Truss analysis loads to consider concurrent
(OP)
Writing this from phone. Please excuse mistakes....
When analyzing a truss what loads are considered concurrently? I thought that I had read for analysis of roof loads we don't have to consider them concurrent, but I can't find hard reference in any codes (or I'm just not looking in right place)!
Thanks guys.
When analyzing a truss what loads are considered concurrently? I thought that I had read for analysis of roof loads we don't have to consider them concurrent, but I can't find hard reference in any codes (or I'm just not looking in right place)!
Thanks guys.






RE: Truss analysis loads to consider concurrent
Off hand, the only one I can think of where you would be right is that we don't combine wind and earthquake.
Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin
RE: Truss analysis loads to consider concurrent
RE: Truss analysis loads to consider concurrent
Would I take the governing loads (typically the snow load) plus any dead loads only ( I thought I had read this someplace) or would I have to consider all forces acting concurrently? I am not designing, I am only analyzing if there is additional capacity.
Thanks
RE: Truss analysis loads to consider concurrent
These would be the various combinations of your dead, snow, wind, etc. that must be checked - each and every combination provided.
RE: Truss analysis loads to consider concurrent
I am basically using the load combination in the ASCE-7 and analyzing from there.
Thanks
RE: Truss analysis loads to consider concurrent
When I plug-in my loads in the load combinations provided in ASCE-07 I am a bit unsure of how to apply.
For instance, 2.4 Load combination number 1 = D + F. Since I am trying to analyze a truss that has top chord DL, and a bottom chord DL, would I just sum the DL's and plug it into the load combinations?
Thanks for the help.
RE: Truss analysis loads to consider concurrent
Apply the load combinations how they are shown in IBC. If you don't have am F then F=0 and your combination would just use dead only.
RE: Truss analysis loads to consider concurrent
I guess this is my path forward.....Once the DLs and LL's are calculated the member size and grade is chosen to resist said loads after the frame is analyzed to determine member forces and stresses. This I can do easily. I get a bit stumped when it comes to actually plugging in Loads into the formulas to determine the worst case scenario of load combination. Since I have 2 DL's (TC and BC) do I just sum them to get "D", then plug in that summarized "D" into the load combinations and determine a total load (worst case of 1-8). then go back and use that Total factored load case to analyze the truss?
Thanks again for the guidance. I appreciate it.
RE: Truss analysis loads to consider concurrent
You need to also consider bracing of the various members, which includes checking the tension chord as a brace for the truss web members, to ensure it is strong and stiff enough for the desired behavior.
RE: Truss analysis loads to consider concurrent
RE: Truss analysis loads to consider concurrent
RE: Truss analysis loads to consider concurrent
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: Truss analysis loads to consider concurrent
For instance, if I tell them that we are in a 60psf GSL area, would they reduce that snow load for the pitch of the roof? Would I determine all loads (Wind, and snow), and convey that to the truss manufacturer? OR would I take the worst case scenario of the load Combo's and tell them that is what I want to truss designed to, plus bottom chord DL, and any additional TC DL?
Just looking to get more insight. Thanks guys.
RE: Truss analysis loads to consider concurrent
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: Truss analysis loads to consider concurrent
RE: Truss analysis loads to consider concurrent