Truss Reactions

[JStructsteel]

So got truss reactions as a lump sum, i.e. not broken into DL, LL, WL, etc.

Is it worth figuring out the components, or just design for the total reaction using ASD?

I asked for the component reactions, but got no reply.

Thanks

 

[JStructsteel]

I can figure it out, but almost any other engineering program can spit out reactions easily. I have a truss girder with alot of different loads, some special loads from partitions, etc.

With edge zones, etc. WL can be a pain too to figure.

Just thought it would be a simple thing to provide.

They did send additional calcs that have some loading broken out.

 

[BAretired]

Since trusses are considered as individual components, there's no way to make one truss take deflection of another truss into account.

There's no way with the software currently in use, but the resulting forces and reactions are clearly wrong as shown. When supports are deflecting, continuous trusses should be avoided in favor of simple spans.

 

[XR250]

There's no way with the software currently in use, but the resulting forces and reactions are clearly wrong as shown. When supports are deflecting, continuous trusses should be avoided in favor of simple spans.

I agree. In this case, I don't think this truss actually works as 2 simple spans. I asked them to try that.

 

[Flotsam7018]

Maybe I am oversimplifying the problem, or maybe I'm just dumb, but can't one just take the tributary load to one truss and use statics to get the reactions by load case?

This is what I do for almost all residential projects, as the percentage of wood truss submittals I see from residential are probably 10%. There are of course notes for a deferred submittal, but I typically get squat.

 

[BAretired]

I agree. In this case, I don't think this truss actually works as 2 simple spans. I asked them to try that.

If it doesn't work as two simple spans, use one simple span. That appears to be the original intent of the fabricator. BCLL is noted as 0.0 psf, with an asterisk beside it, meaning I suppose, that live load between Joint 15 and 17 is not zero. If the truss doesn't work as one or two spans, then it should not be used in this location.

EDIT: Another possibility, if the plan permits is to use a second girder truss at the left side of the attic space. In that way, you could create three simple spans.