2 - Development of CFDST columns

Abstract

Concrete-filled double skin tubular (CFDST) columns have the advantage of being able to resist forces compared to conventional concrete-filled steel tubular (CFST) columns. Other important advantages of CFDST columns include their high strength and bending stiffness, higher fire resistance, and favorable construction ability. A CFDST column consists of two concentric steel tubes with concrete filled between them. Unfortunately, there are no significant applications of this new structural column worldwide, partly due to the lack of design provisions in different design manuals. Accordingly, this chapter focuses on the compressive strength of CFDST columns and is based on published studies of the last two decades. CFDST columns are the currently recommended structural members used in the construction of modern buildings. In this chapter, a review of the research carried out on CFDST columns under axial compression is provided, with emphasis on experimental and finite element (FE) studies. Experimental and FE data have been collected and compiled in a comprehensive table using different parameters found in the literature. This review also highlights, based on up-to-date results, the effects of confinement of concrete, initial imperfection and residual stresses, concrete compaction, hollow ratio, thickness ratio, long-term sustained loading, axial partial compressive loading, preloading on steel tubes, steel fiber-reinforced concrete, and external confinement on the behavior of CFDST columns. Specific emphasis is placed on various design methods of CFDST columns with different cross sections. Generally, it has been recognized that intensive research is still needed for the development of CFDST columns with different cross sections under different parameters.