Steel Shell Roof Structures

The advantages of shell structures for enclosing large, column-free areas are well known. While reinforced concrete has dominated the field of shell construction for many years, recent developments have indicated the feasibility of using steel for certain singly- and doubly-curved roofs. Steel shells are attractive and highly versatile. They are extremely light in weight, well suited to the preassembly of parts, and do not require the elaborate formwork and scaffolding during construction that is associated with concrete shells. Steel shells may be constructed using the standard light gage steel roof deck panels available from many sources in the United States and abroad. A few of the more common panels are shown in cross section in Fig. 1. Used in shell structures, the panels carry normal loads by their flexural strength, but in addition are designed to resist membrane shear loads acting in the plane of their surface. While various shell forms have been built using such panels, there are certain limitations. Standard panels can not be curved much in the direction of their length, and it is not advisable to curve them transversely, except for the most elementary corrugated sections. However, plane subelements can be used as components of curved shells. In addition, most panels can be warped to a certain degree about an axis parallel to their length.