Truss or not a Truss? 7

[Michel60]

I've lurked around the site for a number of years now, offering my $0.02 occasionally (maybe two-bits with inflation and tariff). I now have a question for the group about a proposed truss profile for a residential project where my first reaction is a "hell no", see below. Its 45' long with a maximum depth slightly over 3'-4". To be fair to the truss designer they were asked by the client (without consulting me first, I was assuming that the area would be stick framed) to generate a budget so this is still a fictitious design right now to get to a preliminary cost. The "special trusses" are for a low-slope (<1:12) membrane roof, but the "girder trusses" support about an additional 12' tributary of a 3.5:12 slate roof.

So far I've only seen the profile summary, no calcs. But even with calcs saying it works I'm not inclined to accept the results. I can't imagine that typical truss design software can really handle this problem reliably. I know some of the regulars here have a pretty strong background in plate truss design so my questions to them are:
1) Do you see this as a legitimate truss profile (either typical or girder)?
2) If you do, can the common truss programs out there adequately design something like this?

Thanks!

 

[8thStreet]

Another question - As an EOR - i would love to spot check some truss designs and girders before i show them on my plans. Common items that i need to check are large girder trusses with loads above and scissor trusses for deflection. I dont want to get down the road to construction and then have the truss designer come back and say it cant be done.

So long intro to simple questions - are there any good programs out there to quickly run truss designs? I have reached out to mitek but they dont seem interested in selling their software to people who dont make trusses.

Thanks,

 

[phamENG]

Best luck I've had is talking with a local truss shop. Depends how busy they are and how much competition is around, but I've had luck getting preliminary truss designs with a promise to specify them as the manufacturer. It's even easier when the GC is picked early and they have a go-to supplier I can call. Some are pretty excited when engineers want their input early - seems there a few amongst us who have a tendency to produce less-than-buildable layouts, and any effort to prevent the headache on their end is welcome.

 

[KootK]

So long intro to simple questions - are there any good programs out there to quickly run truss designs?

For my EOR estimates, I just use RISA etc and limit myself to #2 SPF for the chords. The #2 SPF tends to keep the designs from being overly aggressive such that plating issues are pretty much non-existent for 2X trusses. This is a good way to keep yourself from doing silly EOR stuff with the trusses as well.

 

[ANE91]

are there any good programs out there to quickly run truss designs

I have high hopes for Paragon. Try their free module and report back!