Design of Conventional- and Extended-Single-Plate Connections: AISC's New Design Procedures

Abstract

The geometry of a single-plate connection is really quite simple — a rectangular plate is fillet welded to a support, and field-bolted to a beam. But the simple elegance of this connection can often be overshadowed by the complexity of the structural model. The force distribution on this connection is indeterminate, and the connection itself, being relatively stiff, has inelastic features that are important to its performance. Unlike many of the other types of connections, shear tabs rely upon inelastic deformation of the plate to achieve the level of rotation that allows it to be considered a simple connection by the definitions presented in the AISC Specification. The complexity of the inelastic performance of shear tab connections prompted the AISC Committee on Manuals and Textbooks to develop the new, largely prescriptive design procedure now found in the Steel Construction Manual , 13 th Edition. The Manual presents two newly developed design procedures — one that is a refinement of older procedures for the design of the classic shear tab connection, now called conventional single-plate connections, and an entirely new design procedure for other applications, termed extended single-plate connections in the Manual . Like all simple shear connections, single-plate shear connections have some level of restraint and a corresponding eccentricity on the connection. This restraint is largely relieved before the connection reaches its ultimate strength through both elastic deformations, such as flexing of the plate and bending of the supporting member, and inelastic deformations associated with the movement of the bolts as they shift in the holes. As the ultimate load is approached, the bolt holes deform in the plate, providing relief to much of the eccentricity of load.