Rigidified corrugated structure

Claim 1

A RIGIDIFIELD CORRUGATED STRUCTURE COMPRISING A SHEET MATERIAL FORMED INTO COMPOUND CORRUGATIONS INCLUDING A SUCCESSION OF PARALLEL, EQUALLY SPACED PRIMARY CORRUGATIONS EXTENDING TRANSVERSELY OF THE SHEET MATERIAL BETWEEN TWO OPPOSITE EDGES OF SAID MATERIAL AND EACH SAID CORRUGATION HAVING TOP AND BOTTOM PORTIONS WITH WALLS THEREBETWEEN, PLURALITY OF LONGITUDINALLY DISPOSED SECONDARY CORRGUATIONS IN PARALLEL, EQUALLY SPACED RELATION IN THE PRIMARY CORRUGATIONS, SAID SECONDARY CORRUGATIONS HAVING TOP AND BOTTOM PORTIONS AND WALL THEREBETWEEN, THE ADJACENT SECONDARY CORRUGATION WALLS BEING EQUALLY SPACED THROUGHOUT, SAID SECONDARY CORRUGATIONS EACH BEING CONTINUOUS IN AND BETWEEN THE PRIMARY CORRUGATION TOP AND BOTTOM PORTIONS AND WALLS AND EXTENDING BETWEEN THE OTHER PAIR OF OPPOSED EDGES OF THE SHEET MATERIAL, THE EXTREMITIES OF THE COMPOUND CORRUATIONS ON EACH SIDE OF THE CORRUGATED STRUCTURE CONSTITUTING TO AND BOTTOM CRESTS, THE CRESTS ON EACH SIDE DEFINING A PLANE WITH SAID PLANES BEING PARALLEL AND SPACED APART THE HEIGHT OF THE CORRUGATED STRUCTURE, THE HEIGHT OF THE FIRST MENTIONED CORRUGATION WALLS BEING LESS THAN THE HEIGHT OF THE CORRUGATED STRUCTURE, THE TOP AND BOTTOM CRESTS OF THE COMPOUND CORRUGATIONS HAVING BEEN FORMED ON OPPOSITE SIDES OF A NEUTRAL PLANE.