r/StructuralEngineering • u/SEhell • 8d ago

Structural Analysis/Design What software is best for designing railway catenary support frames with eccentric connections?

I’m designing railway catenary support frames, usually single-cantilever posts with a beam carrying the cables. In some cases, the frame is built up from channels and diagonal members.

I’ve used RAM Elements, but the limitation is that members connect at the centerline. I need software that can model the actual geometry, where members connect to the faces of the sections.

For example, I have a post made of two channels placed face-to-face with a 12" gap, with diagonals connecting to both flanges of each channel. What software would you recommend for analyzing and designing this kind of frame which is similar to these pics?

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u/stressedstrain P.E./S.E. 7d ago

Why can’t you just model a dummy fixed outrigger or something to impart the eccentricity ? There’s also rigid end offsets in RAM you might be able to leverage.

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u/SEhell 7d ago

I tried that by addigning cardinal points but i was able to only shift the chanel flanges but i need the diagonals on both sides, can we do that in RAM elements?

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u/stressedstrain P.E./S.E. 6d ago edited 6d ago

I should’ve been more clear—I actually hate rigid end offsets in RAM and cardinal points and the like as well. They often are misunderstood and are easy to miss when trying to diagnose why a model isn’t behaving as expected.

If you really think it’s needed to consider the eccentricity from loading a channel via its face versus its shear center, as i was suggesting above, I’d model very short (weightless) steel outriggers a few inches long from your channel to where the cable frames into and that will create the resulting torsional effect you’re desiring. Then just ignore these for design.

Alternatively keep things framed as you have already an just apply a uniformly distributed torsional load to the channel that is equal to applied load times offset from shear center to channel face.

I might be misunderstanding what you’re trying to do but that’s my 2 cents.

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u/t4m4 7d ago

SAP2000 allows for eccentric connections, but I have never worked with cables.

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u/SEhell 7d ago

Can it do for both side of members? I modelled this in RAM elements by assigning cardinal points, with this i was able to shift he flanges of the channels but i need to add the diagonals on both flanges. Is there a way i can do in Ram elements? Or can SAP2000 do this?