Behavior of Polygonal and Circular Ring Beams

In this paper, expressions for rotational stiffness of polygonal and circular rings are derived and interpreted, and results are also presented graphically as design aids. A special study of the effects of warping is presented. The substantial increase in overall stiffness of the ring due to warping is evaluated and a chart is given for practical use. Two numerical examples in which evaluation of the rotational restraints of the rings are given, and the results used in the analysis of the roof girder under service loads, refer to an actual structure. A comparison made with the results of a conventional analysis which ignores the rotational restraints of the rings shows a desirable reduction of approximately 10% in the moments, rotations, and deflection of the girder. In addition, it is shown that an elastic redistribution of moments occurs in the ring beams as a result of rotation of the supporting radial girders.