Need to strenghten my shop windows. We have an inch square section steel that runs vertically through the windows on the inside.
On the rare instance that we get a north window the whole lot moves. The easiest remedy is to pay someone to put another square tube above the big windows on the outside and bolt the wood to it. It is 3.4 m across. I reckon it would have to be bloody big not to flex. It would however support the weight of the upper section making it less likely to collapse in a hurricane.
Otherwise I will have to fit some steel at an angle to brace the inside steel.

I’m no sructural engineer, but that looks like it is close to needing proper support with an RSJ and correctly specced toughened glass etc.

Maybe there some builder types who can advise more betterer 😉

The only answer here is “it depends”.

I would also want to check that the lintel above the window is adequately strong that you don’t actually need to support the load above.

It will always flex a bit, although that part does look quite puny.

When one of the windows was smashed the repairer has his ladder propped on the centre bit. This was pre steel and it didn’t collapse.
I did advise him that it wasn’t a good idea.
Also when a man parked a Ducati 900ss outside on the path I did ask him not to rev it too much when he started it!

Id have thought that a RHS vertical behind the mullion fixed to the floor and the lintel above with connection to the existing cross member would be better as it’d be shorter and allow you to fix at several points.

50x50mm section will hardly flex over that span I’d have thought. You only need to reduce flex not eliminate it. don’t you?

Or, you could build a small stud wall/buttress 30cm deep from floor to ceiling. You’ve already got the bookcase there so it should be an issue visually.

Have sourced a 4 metre length of 50 mm square aluminium tube. It might be too visible from the outside so looking to place it inside.
The weak part has always been attaching it to the vertical 25mm steel on the inside. The inside steel is screwed into wood at each end.
I’m thinking that I should take the vertical out , fit the 50mm section, attach wooden window frame to section and then maybe attach the vertical to the horizontal.
Would I even need the vertical?

I think a steel cross like a crucifix would be the most effectice. Or another idea would be secondary glazing behind the existing window which could be fixed to the original frame, much more secure, easier to clean and warmer.
It’s got to be on the inside though. It’s a nice old window and I have to walk past it!

Lets hope it’s still in one piece on Monday morning!

I’d go with what aP said.
Cut it to fit floor to lintel & a plate on each end, fasten it to the floor & lintel, then through into the frame at intervals.