Abstract: A high-strength tubular beam of folded corrugated cardboard, for example for constructing disposable load-carrying platforms, comprising a single corrugated cardboard sheet (1) folded back several times on itself to form an overall section of right angled or isosceles trapezium form (4, 6', 8', 8, 6), divided into two adjacent rectangular or rectangular trapezium half sections (4, 6', 8', 18'), (4, 6, 8, 18), each comprising two mutually inverted triangular channel configurations (16', 14', 12')-(8', 10', 12'), (10, 8, 12)-(16, 14, 12), which mate with each other and have a common diagonal (12, 12').