King Post Truss System Cuts Roof Framing Cost by 30%

by Charles H. Thornton, (A.M.ASCE), Pres.; Lev Zetlin Assocs., New York, N.Y.,
Paul A. Gossen, (A.M.ASCE), Project Dir.; Lev Zetlin Assocs., New York, N.Y.,

Serial Information: Civil Engineering—ASCE, 1977, Vol. 47, Issue 6, Pg. 49-51

Document Type: Feature article


The design was based on requirements for minimally obstructed sight lines (Robin Hood Dell Open-Air Theater, Philadelphia, Pa.) for outdoor seating and a tight construction budget of $4,500,000. The resulting steel roof framing system, incorporating a two-way 32-ft (10-m) deep system of kingpost trusses, weighs 9.5 psf (455 N/m²) compared to about 13 psf (623 N/m²) for conventionally trussed structures, or a cost saving of 30%. Rigidity is provided by using the triangulated sloped walls of the stagehouse as trusses to stabilize the roof over the seating while supporting the stagehouse roof and gridiron. Wind resistance is provided by the stagehouse trussed walls and roof and the six tubular columns at the north facade of the building. To make maximum use of girder capacity the main king post trusses were post-tensioned after erection by jacks at the top of the post. The roof shored during erection, was slowly lifted from its temporary supports during jacking, thus achieving its final force configuration.

Subject Headings: Trusses | Roofs | Frames | Steel structures | Walls | Public buildings | Budgets | Steel frames | Philadelphia | Pennsylvania | United States

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