grillage

n.
A network or frame of timber or steel serving as a foundation, usually on ground that is wet or soft.

[French, from Old French, trellis, from greille, gridiron. See grill.]

1. A framework of heavy timbers, steel, or reinforced concrete beams laid longitudinally and crossed by similar members laid upon them to spread a heavy load over a larger area, esp. for use where the ground is not firm.
2. A series of steel beams, bolted together and placed over a footing; used to distribute a concentrated column load over the top of the footing.

grillage, 2

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