50 & 20 Years Ago
Unusual Television Studio
The building illustrated is clad with 85 tons of sheet lead – chosen for its sound insulating qualities – coloured a soft grey. The cantilever doubly curved roof is a steel space truss: three arches in high tensile steel span the building between two concrete piers. The arches have tapered wide flange cross sections which have a maximum depth of 27 in at the apexes.
The steel space truss resists the roof deadload of a 4 in thick lightweight concrete slab: this is cast on steel mesh and finishes flush with the top surface.
Under live load the concrete roof and supporting space trusses act compositely.
Steel tubes – maximum diameter 8 in – for extra heavy cross sections form the longitudinal, diagonal and edge members of the cantilever spans. Gusset plates at the connections of the tube resist shear stresses between truss and concrete deck, so ensuring composite action. The building is in Marina City, Chicago and was designed by Bernard Goldberg Associates, architect-engineers of that city. The unusual roof was designed by Hannskarl Bandel, Severud Associates, New York.
Reprinted from Volume 5 No. 3