Is this strong enough

[Kent]

I cant say because it depends...
However i dont like the staight verticle type of the back with the there or thereabouts 90 degree arms
I should be very wary of the rack dropping a few lengths onto you when pulling a length off or heaven forbid the rack comming over onto a person.
My own rack is 40x40x5 but carries its load into the wall and floor.. The carry arms can be divided which gives a very high total load over the amount i could reasonably put onto each layer.

In short its not so much the section but the design and where it puts the load as regsrds direction

If you are unsure perhaps consider getting itinspected.?

At the very least put something on the arm ends to stop the materials spilling off the arms?

 

[Richard.]

It’s industry standard on structural joints to weld all round box section. It’s stated on nearly every welding drawing I’ve looked at with the exceptions being interference usually.
A weld tear will nearly always propagate from either a defect or a start/stop. If you take away the start stop by closing up you eliminate some of the risk. Leaving a gap to allow a joint movement and reduce rigidity is all very well but that movement will put more pressure on the welds in place and they will more likely tear from the weakest point. The start would be my guess. You want the box to bend before the weld fails so a good structure will be welded strong to ensure this happens then designed well to avoid the box section bending. I don’t disagree the T pieces are a good idea to take load off the weld but I don’t agree only welding 2 sides makes for a better joint.
You’ve also got to consider internal corrosion if you leave gaps and moisture manages to work it’s way in there. Close em up I say.

 

[Kent]

It’s industry standard on structural joints to weld all round box section. It’s stated on nearly every welding drawing I’ve looked at with the exceptions being interference usually.
A weld tear will nearly always propagate from either a defect or a start/stop. If you take away the start stop by closing up you eliminate some of the risk. Leaving a gap to allow a joint movement and reduce rigidity is all very well but that movement will put more pressure on the welds in place and they will more likely tear from the weakest point. The start would be my guess. You want the box to bend before the weld fails so a good structure will be welded strong to ensure this happens then designed well to avoid the box section bending. I don’t disagree the T pieces are a good idea to take load off the weld but I don’t agree only welding 2 sides makes for a better joint.
You’ve also got to consider internal corrosion if you leave gaps and moisture manages to work it’s way in there. Close em up I say.

Yep the only reason to not fully weld doesn't apply to these shs joints and thats adding a stress riser fixing crack repairs with lozenge shaoed fish plates etc
Box welded either side as rack arms will imo almost definitely fail by tearing down the haz starting from tge top