Is it allowed to install support to bottom flange of crane beam?

If it was designed for it and the girder will meet the strength and performance specs of the crane, sure. Probably not a great idea, though.

Now, if you're asking about specific prohibitions in some particular, unmentioned code: I don't know.

I have never seen anything like that before. I assume the Owner knows the bridge crane should not be used at the same time something is hanging from one of those brackets.

DaveAtkins

I might be looking at the wrong thing, I think perspective is throwing me off a bit. Those look like they might be intended as cable tray or small pipe supports. I don't love it, but at a low load it's likely not going to cause a catastrophic problem. I could also see a situation where that's a small load and it's uneconomical to pick up the number of required supports another way. That being said, I wouldn't use an L support in that situation. I'd be using something that doesn't torque the beam.

This feels like a situation that happens when a piping or electrical drafter calls out a routing and typical support type without a structural person having an opinion on it.