Ultimate strength of concrete filled square steel tubular beam-columns: Required conditions for attainment of full plastic moment and framework and issues of strength design

The objective of this study is to propose the axial load ratio-slenderness ratio relations which assure that strengths of CFT beam-columns attain the full plastic moment. CFT beam-columns subjected to constant vertical load and monotonic increasing moment are analyzed and the maximum strengths are obtained, taking the moment gradient ratio, the value of α and strengths of materials as analytical parameter. After examining the effects of parameters on the maximum strength, required conditions for attainment of full plastic moment are consequently summarized as Eqs. (12)-(15). Moreover, the framework and issues to solve of the strength design are presented. © 2020 Architectural Institute of Japan. All rights reserved.