David Sharpe
"An Aircraft Hangar and the Study of Long-Span Metal Structures" (MS 1962)
Advisor: Myron Goldsmith
Structural Advisor: Fazlur Khan
Material: Steel
Structural system: Continuous rigid bent system
Maximum span: 168 feet
“In the lower span ranges, the curves tend to coincide and it can be concluded that for these spans, it does not matter very much which structural type is used. But in the upper span ranges the curves radically diverge.”
The thesis projects of David Sharpe and Phyllis Lambert were collaborative, two-part exercises. The first part began with each independently developing a solution for the design problem of an aircraft hangar. The second part was a deeper study of long-spans structures, which was presented in two parts. Sharpe’s thesis explained the study of long spans in metal, and Lambert’s in concrete. Both were advancements of the principle developed in Goldsmith’s 1953 thesis, that every structural type has an appropriate maximum and minimum size.
Sharpe’s hangar is a 232 ft. x 516 ft all-glass enclosure. A continuous bent system on 42 ft. centers was selected to accommodate three 170 ft. hangar bays. 6 ft. deep built-up plate girders rigidly connected to four cross-shaped columns each comprise the longitudinal bents. The structure is braced transversely with shallow bent beams at 8 ft. on center, and 2 ft. deep beams at column lines. The bent beams provide for roof pitch required by code for glass roofs to let light in at all points within the hangar. The structure was planned to accommodate future expansion.
In the research component, Sharpe developed a composite graph showing the relative efficiency of different types of structure in terms of the weight of material, and demonstrating that the structural system is critical in longer spans. One of his surprising findings was that arches are lighter than domes for comparable structural systems. His thesis highlights the importance of welding in creating full-strength rigid connections and, though not yet common, that high strength steel would provide great savings in material. The ultimate (material) economy in metal long-span structures studied was geodesic domes utilizing tubular members. He also pointed out that meaningful analysis was complicated because “different materials and even the same materials in different structures have different costs.”
