Restoring force characteristic model on bending moment-rotation angle relationship of concrete-filled square steel tube beam-columns

This paper proposes a new simplified restoring force characteristic model of a bending moment-rotation angle relationship for concrete-filled square steel tube beam-columns from short to slender. In the proposed model, each flexural strength is calculated by a general superposed strength method, and new multiple regression formulas for each rotation angle are proposed based on results of cyclic and monotonic loading tests from previous researches. Predictions from the model of the bending moment-rotation angle relationship are found to agree approximately with experimental results up to large rotation angles. © 2021 Architectural Institute of Japan. All rights reserved.