Plastic Analysis of Circular Balcony Girders

A plastic analysis was made for balcony (or bow) girders of circular arc with a subtended angle of not more than 180○ and of constant cross section, fixed at both ends and subjected to uniform load perpendicular to the plane of the arc. The problem had been solved previously by Boulton and Boonsukha. But the method introduced herein, being developed independently, contains several new features, and the results presented are more extensive. First, the general method of analysis was examined. Next, various mechanisms of failure were investigated. It was found that failure was possible only for the mechanisms with two, three, or four plastic hinges. A chart was given for determining the limiting values of β (ratio of fully plastic torque to fully plastic moment of the section) for the three mechanisms of failure. Finally, the collapse loads for various values of subtended angles and various values of β were presented in a chart that may be useful to engineers interested in plastic (or limit) design of balcony girders.