Comparison and design of stiffened rectangular concrete-filled steel tubular members

Abstract

A stiffened rectangular concrete-filled steel tubular (CFST) member offers improved composite action over the unstiffened counterpart in terms of delaying local buckling of the rectangular steel tube and enhancing confinement to the infilled concrete, and thus various stiffening forms were proposed. Choosing an appropriate stiffener in practical design needs comprehensive understanding and comparison on the efficiency of various stiffeners. However, most studies focused on a single type of stiffener only, no guidance was provided on how to account for the benefits of stiffened rectangular CFST members in mainstream design specifications, and no unified calculation method for load capacity was formed. In this work, finite element models for stiffened rectangular CFST members were established and verified by test results. Then parametric analyses were conducted to compare the axial compressive and flexural behavior of rectangular CFST members with various types of stiffeners. The appropriate arrangement and detailing of stiffeners were proposed, and the diagonal ribs showed the best performance under the same material strength and steel consumption. Finally, mechanics-based models and unified calculation methods were proposed to calculate the axial compression and interaction strength, and were found to well predict the strength of stiffened and unstiffened CFST members. These results will further facilitate the use of stiffened rectangular CFST members in practical engineering projects.