Design of Top Chord of Stressed-Arch Frames

Abstract

Stressed-arch frames are characterized by a posttensioning procedure that is used to erect the frames from an assembled configuration at ground level to a final erected shape. During the erection process, the top chord becomes curved and is usually stressed into the inelastic range. Consequently, the strength of the erected frame under service loading cannot be assessed rationally using conventional elastic or plastic methods for the analysis and design of steel structures. The purpose of this paper is to examine in detail the provisions of the Australian Standard for Steel Structures, AS4100-1990, and the 1993 American Institute of Steel Construction Load and Resistance Factor Design Specification (AISC LRFD) for the design of the top chord of stressed-arch frames, and to propose and validate a simple design procedure. In particular, the irrationality of design based on conventional elastic and plastic methods, and, alternatively, the rationality of design based on advanced analysis as described in AS4100-1990, is identified.