So I'd say
that you should never use particle board to carry loads.
Manufacturers of computer
room raised floors will disagree with that
-- all the high-load ones I've ever coma across are made of particle
board (usually with a very thin metal cladding, which is to protect
against moisture and impacts, and to provide electrical continuity).
Of course, these are 35mm-45mm thick, not 15mm-18mm.
They also are supported around the whole edge of a two-foot-square
square. If those shelves were supported every two feet - especially if
they used that kind of thickness - I bet they'd still be just fine.
From an engineering perspective, I'd say that
particleboard is fine for
carrying loads in the right circumstances, but it is
incumbent upon the
designer to know what those circumstances are and design accordingly.
Building codes (which were cited in support of the notion) tend to be
conservative, and (especially given the likely blind substitution of
particleboard for plywood) I'm not surprised they take the tack
described.
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