I-Joist Truss

[Yt.]

Is it technically possible to design an i-joist truss? If possible can give me some guide about joint design for i-joist? and axial behaviour?

I would like to design a i-joist truss for a 12m span if posible. But prior to deeply search about it i'll like yours opinion about the reliability of a design like this.

Thanks!

 

[jayrod12]

I'm sure it's possible, but why?

There are certainly cheaper and more acceptable ways to build a truss capable of spanning 12m

 

[JohnnnyBoy]

I'm not really sure why this would be any different than designing I-joists for a floor system. I would take a look first at any I-joist manufacturer and see if your span would be too large, and check your loading in comparison. I would also ensure that you have tie down straps for your roof joists to counteract any uplift forces on your roof.

 

[Yt.]

Thanks for your answers,

It's not a roof, perhaps i'm not translating this properly but i refer to that kind of structure, mainly axial pinned elements. I need it to do another work for a couple of weeks. The simple supported i-joist isn't strong enough even if I pray for a support at 6m, also i have the difficulty that it need to be hand installed so i tough i-joist may result in a low enough weight.

I haven't seen any table or document about axial buckling or strengths capacity, neither if it'll be full cross section or effective. At joints maybe i'll could manage to avoid cantilevered fastener by placing a sufficiently rigid attached plywood to the OSB web, (haven't reviewed OSB fastening yet, just steel, ply and concrete).

I'll be pleased if some one let me know about i-joist axial behaviour. I made a regular search about it and found nothing.
Regards,

 

[msquared48]

I can see a whole host of member lateral stability and connection problems here.

Every connection would have to have web stiffeners and side plates.

I do not think I joists have ever been analyzed as columns, let alone used as such.

Bad idea... Bad... Bad.

Mike McCann, PE, SE (WA)

 

[Yt.]

Thanks msquared48,

I think the same about it, there'll be plenty of things to handle, but i-joist are already used with slopes at roofs, so there should be something about compression performance.

 

[jayrod12]

Sloped I-joists are intended to be treated like bending members as far as I am aware. I.E. pin-roller supports.

 

[Yt.]

Thanks jayrod12, that's also the perception i got after reviewing some tables. But there is axial behaviour when i-joist are sloped.

Anyway, yours answers let me clear that there is low reliability about a design like this.

 

[HouseBoy]

I also think that I-joist rafters are limited to 12/12 slope due to a concern about axial compression.
Pretty are that was a limitations many years ago but don't know if they have updated that in recent years.