Inelastic Limit States Design. Part I: Planar Frame Studies

TLDR

Advanced inelastic analysis methods enable realistic limit‑state design of steel structures under load and resistance factor specifications. The study summarizes the in‑plane behavior of low‑rise steel frames. Second‑order inelastic analyses were used to design and compare low‑rise frames against conventional elastic methods, and a representative design was evaluated for strength and serviceability compliance. Second‑order concentrated plasticity analysis accurately models system behavior, proving effective for steel design and revealing benefits, current status, and future directions. A companion paper presents the method applied to a three‑dimensional multistory frame.

Abstract

In conjunction with load and resistance factor design specifications, advanced methods of inelastic analysis afford the opportunity to design steel structures based on realistic assessments of limit state behavior. This paper presents a summary of a study of the in‐plane behavior of a series of low‐rise frames. Designs are obtained that rely on a second‐order inelastic analysis to demonstrate that the frame and its members are adequate in resisting the effects of factored loads. The inelastic designs are compared with designs obtained using conventional elastic methods of design. A representative inelastic design is further evaluated with respect to strength and serviceability limit state behavior, including conformance with current load and resistance factor design specification provisions. The accuracy and reliability of using a second‐order concentrated plasticity analysis to model system behavior are also established. The investigation indicates that second‐order inelastic analysis can be used effectively to design steel structures. It also identifies the benefits, current status, and future directions for applying inelastic analysis in design. Use of the inelastic analysis/design method for a three‐dimensional multistory frame is presented in a companion paper.