Bending Under Seated Connections

The seat, or bracket, is a common type of connection in structural steel. A bracket carried by a column or beam web or, in general, by a vertical plate, throws a bending moment into the supporting plate, and if the plate is relatively thin it may be overstressed. No data about this important effect are given in the AISC Manual of Steel Construction or in readily available reference works; yet this stress may be critical and govern the design of the connection. The problem of evaluating these stresses arose in the analysis of numerous heavily loaded brackets used in the Vertical Assembly Building at Cape Kennedy, designed by Urbahn-Roberts-Seelye-Moran (URSAM). A theoretical investigation of plate bending under brackets has been carried out by both an elastic method and a plastic method. This paper presents the results of these analyses, including a rule of thumb as well as more accurate methods of computation.