Effect of ultra-high strength steel on mitigation of non-ductile yielding of concrete-filled double-skin columns

Concrete-filled tubular (CFT) sections, and the most recent configuration of these sections, concrete-filled double-skin tubular (CFDST) sections, can provide high strength in structural construction. In this study, an innovative fabrication strategy is proposed to prohibit the non-ductile yielding of CFDST sections by applying ultra-high strength steel corner steel tubes. Hence, the static compressive behaviour of CFDST columns containing ultra-high strength steel tubes is experimentally investigated. The results are then compared with those for the same experiment conducted on a CFDST specimen with corner mild steel tubes. In addition, a numerical investigation is conducted to examine the effect of different parameters on promoting the ductility and compressive strength. In order to pave the way for utilizing CFDSTs with corner tubes in engineering practice, a simple analytical formulation is also proposed to predict the load-displacement relationship of these sections based on the experimental and numerical results.