Types and Forms of Shell Structures

THREE SEGMENT FOLDED PLATE

This sketch shows a folded plate structure with three segments for each barrel. The end stiffeners are rigid frames rather than deep girders as in the last example. The forces from the reactions of the sloping plates on these rigid frames will be quire large and at an outside column they will not be balanced by thrusts from the adjacent plates. The size of the frames may be reduced by using a steel tie between the tops of the columns which can be concealed in the fenestration.

The dimensions of the plates are dependent on both the width of the barrel and on the span. The depth of the shell should be about 0.10 times the span and the maximum slope of a plate should not be greater than 40 degrees. For example, assume for the above structure that the span is 60 feet and the bay width is 24 feet. The depth of the shell should be about 6 feet and the horizontal width of each plate with a three segment plate should be about 8 feet. The slope of the plates is 6/8, which is about 37 degrees and is satisfactory. The thickness of the plates could be about 3 ½ inches.