Conceptual design of hanging railway overhead support.

[Tom Karsten]

In uni we have to design a hanging steel structure connected to an existing bridge to support a new railway overhead line. The forces acting on the structure are coming from the overhead line due to self weight, wind load and temperature, and are all acting in the plane of the structure. The structure will be connected to the existing beam by welding or clamping (relying on friction force) with bolts and tension rods connected to a plate on the other side of the beam.

I was wondering what the advantages and disadvantages are of both conceptual designs shown below and why one would prefer the left or right design. I do find examples of both in real world examples but upside down with support masts clamped at the bottom.

Thank you for the expertise!

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[Smoulder]

Left: can be a portal frame so only pin connections to existing beam. Need a second leg.

Right: Needs fixed connection to existing beam. Thin diag brace only works in one direction. Not a good concept if load can reverse. Otherwise could have pin connections in the new structure.

Pin connections to existing usually turn out easier (left concept). Fixed connections in the new structure done off site where extra work not a problem.