Steel box section strength
121 cm. Back edge and sides well supported.
Then 20mm x40mm with 3mm wall will be fine - use 2 lengths - front and
middle.
Obviously the 20mm is in the important vertical direction. Also, the metal
companies seem keen of "16" gauge, which they suggest is 1.5mm, rather than
3mm. Is this well underspecced? Does anyone publish formulae?
Christian.
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