Ultimate flexural strength of rectangular concrete‐filled steel tubular beam‐columns using high‐strength materials

Abstract

AbstractThe ultimate flexural strength of concrete‐filled steel tubular (CFST) beam‐columns is calculated using the full‐plastic strength as per the “AIJ Recommendations for Design and Construction of Concrete Filled Steel Tubular Structures”. However, the full‐plastic strength might overestimate the ultimate strength of rectangular CFST beam‐columns, when the width‐to‐thickness ratio is significant and/or high‐strength materials are used. The calculation of the ultimate flexural strength when it exceeds the applicable range of AIJ CFT recommendations is based on a method that considers the stress reduction on the compression side of the steel tube or outermost edge strain of the concrete. However, both stress reduction and outermost edge strain should be considered when high‐strength materials are used in CFST for accurate ultimate strength formulas. In this study, a simple evaluation method for the ultimate flexural strength of rectangular CFST beam‐columns was proposed using the maximum strain at the extreme concrete compression fiber and stress reduction on the compression side of the steel tube. In addition, the appropriate strain at the extreme concrete fiber needed to accurately calculate the ultimate strength was discussed.