Some Help with Basic Beam Design

From the diagram, the diagonal struts meet the supporting struts at an angle, so at these joints there is shear stress. In B, the angle is closer to perpendicular than in A, so B would have less shear stress than A.

Shear is not the limiting force, I suspect. I always see framing to the C/L of the members, as in A, as PapaDoc states. A is correct. B is a mistake.

As I see it the function of the infrastructure is to transfer weight to supporting wall/post/ground...The greatest point of deflection or weakest point would be the center of the horizontal cross beam...the arch roof is transferring weight to the supporting beams to ground and also supporting the center of the vertical beam at the weakest point of the horizontal beam...the diagonal support beams should not be trying to support the roof by using the horizontal beam but the center vertical beam....so the second one I think is the better design...

Even better...

https://www.archtypestructures.com/buildingshellsystem.aspx

Make the centerlines of the members intersect at a common point. That would reduce secondary stresses and make the structure able to support more load. "A" seems to do that.

I thought that this would be a very easy and basic question. But we have several answers on both sides.

CCOOP609 has gotten his answer voted as a Good Answer, though. And frankly, he most sounds like he knows what he's talking about. I do however appreciate everyone's input. I still would like some feedback though... if any would like to chime in.

Meanwhile, I'm going to go ahead and design my structure using model "A" , as CCOOP suggested... with the added struts on each end, as SolarEagle suggested in his reconfiguration of my original model "B". The one that looks similar to an M, although with all the radial struts resting on the horizontal beam.

Comments are welcome.

I will, in the end, be sending my drawings to a PE in order to get the drawing certified. So, he'll tell me if it's fine before we build it, but I'd rather send him the proper configuration to start with, rather than have to change it around after he looks at it.

Thanx again for everyone's help.

FYI, this is going to be an awning and the structural members are going to be aluminum rectangular tubing... probably 1" x 2"

Thanx all, for all the reference material and suggestions. Here is what I came up with and turned in. Different project than my first example, but I have a number of arches to design. This truss configuration is called "Bowstring".

REV: 001

You will probably find out that just like the Romans in stone, that you won’t need any of those truss elements, unless you are running heavy truck traffic across the bottom.

You might also need some plan for holding the roof down in high winds...such as a tie down assy....here we just use like 1/8"-3/16" stainless wire anchored to the floor with eyebolts run across the panels...

https://www.metalconstructionnews.com/articles/top-mistakes-by-metal-roof-installers

Has anyone noticed that it is only 10 ft across? ...and the truss is made of small aluminum tubing?

https://www.mbci.com/products/roof/curved-roof-systems/curved-battenlok-/

Correct. It's the snow load that is the issue. That, combined with the fact that I'm trying to keep that small aluminum tubing as small as possible.

Roger that....maybe you could add some heat..?

What zone are you located... I was just working on something similar,...

For the live load requirements, What zone are you located?...

for the horizontal I normally use this calculation for deflection... L/360 or L/180.. depending.

Unfortunately, this doesn't have a arc...