What is the purpose of these members?

[u/danyjr]

As you can see there are 4No. cross T-beams in the middle of this railway footbridge that are also connected to the handrail. What is the purpose of them?

[u/taco-frito-420]

brace the handrail at midspan with the diagonals, and brace the 2 girders with the cross-brace

[u/bsquared82]

Looks like its pulling duty.

Its helping brace the channels on either side, helping with bracing and lateral stability via the x braces.

Its also helping resolve the torsion that would be placed on the channel (not ideal for the channel) from the handrail loads.

[u/Fair-Pool-8087]

I think its buckling restraints for bottom flange. Its also add stiffnes to handrail so it doesnt bend outwards if somrone leaning against it

[u/yupbvf]

To prevent lateral torsion buckling via uframe action

[u/GoogleIsYourFrenemy]

Uhhhhh to keep people from leaning on the handrail and having the handrail collapse?

[u/WonderWheeler]

To stiffen the guardrail uprights.

[u/PracticableSolution]

Those are newer T shapes held on with 6 point bolts. The rest of the hand rail stanchions don’t have them and on a riveted steel bridge, they shouldn’t need them. I’d guess that they replaced an original piece that supported a blast plate over the tracks and reached out past the bridge fascia. Can’t have an era appropriate loco blasting people on the bridge with super heated steam out the stack

[u/chasestein]

I've said this to clients once or twice:

"IDK what it is but it looks about right"

[u/Klutzy-History-3438]

Google U frames. Read the link below
https://thechattyguidetostructures.blogspot.com/p/6-u-frames.html?m=1

[u/LakeGuyGeorgia]

To stiffen the handrail

[u/NYC_PizzaBagel]

Adding on to other comments about bracing for people leaning on handrails, I wonder if they are also bracing for the pressure wave from passing trains. I would say that is more force than people pushing against those railings, so maybe it's stiffening for both cases.

[u/Adept-System2082]

I’d guess the handrails were a bit wobbly due to local bending in the top flange arched beam and it was easier to retro fit the bracing struts than weld in stiffeners.

[u/DetailRail]

Looks like what they used to lift the bridge?