Haunched connections are widely used in rigid frame structures, affording a pleasing appearance and, at the same time, enabling a reduction in the size of main structural members. The recent development of design procedures based on the behavior of steel in the plastic range has emphasized the need for more information concerning the plastic behavior of haunched connections. It is the purpose of this Bulletin to present design procedures for proportioning both tapered haunched connections and curved knee connections, based on the principles of plastic theory.

The Bulletin is divided into three parts. In Part I, a theoretical design procedure is developed for tapered haunched connections, and in Part II, a similar theoretical procedure is developed for curved knee connections. The effects of axial force and shear upon the plastic moment capacity of sections within the haunch are taken into account. Also, the stability of the compression flanges is considered. Examples illustrating the design methods for the two types of haunched connections are presented. Part III is a detailed report of tests performed for the purpose of evaluating the concepts and design procedures presented in Parts I and II.