Please classify this Steel Web Truss
Please classify this Steel Web Truss
(OP)
Hello All Structural Steel experts, I am trying to classify this Steel Web Truss. I have attached the data gathered by our site assessment.



Thanks.



Thanks.






RE: Please classify this Steel Web Truss
Are they cantilevering from the back wall? Big galvanized plate at the back of the truss!
Maybe left over components from a scaffolding/shoring system and "bastardized" to suit.
RE: Please classify this Steel Web Truss
RE: Please classify this Steel Web Truss
Here is a photo of how they are attached at the front of the garage.
RE: Please classify this Steel Web Truss
Some 'funky' connection (or lack of) at this detail:
RE: Please classify this Steel Web Truss
RE: Please classify this Steel Web Truss
So you'd have to either sample and test pieces of these members or it seems like you might need to load test this to know for sure.
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RE: Please classify this Steel Web Truss
Side note - your diagram of the truss doesn't match the picture. The diagram shows the last web member connecting at the end of the top chord...picture shows the last web member framing in short of the end of the truss. Big difference for the top chord.
RE: Please classify this Steel Web Truss
RE: Please classify this Steel Web Truss
Other Fun Concerns:
I don't think you have any real top chord bracing. by the photos it looks like your bottom chord is not braced which means your truss model doesn't work.... Bar joists need bottom chord bracing for the compression-web model to work properly.
Diaphragm?
Wall Capacity?
To be honest, you are going to have to say that this is not adequate for any additional loads and you cannot verify if it can support existing loads at this time.
RE: Please classify this Steel Web Truss
Picture for comparison:
As pointed out earlier, there are insufficient/missing chord ties for this "system" to have any real design strength.
RE: Please classify this Steel Web Truss
RE: Please classify this Steel Web Truss
RE: Please classify this Steel Web Truss
- you have top chord bracing at 2' o/c.
- with CHS top chord and end rotation restraints you can probably get by without bottom chord bracing for gravity load at least.
- webs shouldn't give you any grief as they're pretty stocky relative to the flanges.
- At 38, span to depth ratio is high. But, then, it's 26" on centre steel in a light weight system.
Maybe start with some simple deflection estimates then gauge whether it's worth going any further.
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: Please classify this Steel Web Truss
I think it is important, and it’s certainly time, to sit down with the client, and explain the facts of life. After all, you aren’t a miracle worker, even if he does think you should be. He built it on the cheap and now wants it to meet current code and support added loads, and that’s pretty unreasonable, given that it probably wouldn’t meet min. stds. as is. You’ve got a fair amount of ammunition from the posts above. Ask the client for the original plans specs., design info. and calcs. Ask him for the manuf’ers. name and spec. sheets/shop drawings for the roof trusses. Explain why you need these if he wants his questions answered. We know what the answers will likely be, but he is now asking you to make something out of nothing, and is he willing to give you the free rein to do what needs to be done and to pay you for your time and effort? If he can’t provide the answers and info. you need for a reasonable analysis and investigation, you will need to do material testing, etc. to develop this design info. Make sure that he understands that you are not willing to just act as his reinsurer, or insurer of last resort, just for a small engineering fee.
RE: Please classify this Steel Web Truss
As dhengr says, talk to the owner but suggest adding to the existing "trusses' sufficient added members to at least carry some degree of COMMUTABLE loading, plus assume the lowest working stress for the steel once you have determined tube wall thickness. However, it might be a "good" job to walk away from.