On the design and behavior of axially-compressed square concrete-filled double-skin tubular short columns for ocean engineering applications

Deep-sea offshore wind technology development is now deemed a strategic national need in China. At the same time, research and engineering communities have a substantial increase in intertest on the design and behavior of novel arrangements for double-skin composite columns. Accordingly, concrete-filled double-skin steel tubular (CFDST) columns have recently gained significant importance in wind farm support structures as well as tall buildings with heavy loads. To predict the axial compressive resistance of square CFDST short columns with square inner tubes (SS-CFDST) or circular inner tubes (SC-CFDST), a new design resistance model has been proposed in this paper. First, test data for axially-loaded short columns of SS-CFDST and SC-CFDST configurations were extracted from literature studies. Then, available design resistances in the European and American specifications, as well as from previous studies, were examined, and a range of accuracy results were displayed. Subsequently, new formulae for determining the lateral confining pressure (frp) supplied by outer and inner tubes in different types of square CFDST columns have been developed using the data gathered from the experimental tests. A new design resistance model has then been proposed to calculate the axial compressive resistance of SSCFDST and SC-CFDST short columns, based on the proposed formulae for frp in addition to the confined concrete strength. This has been followed by a finite element (FE) modeling using ABAQUS program that has been well validated, generated to increase the resistance data of these columns. The design formula was then verified through the extensive parametric studies generated by the FE modeling. According to the comparisons between numerical and proposed resistances, the design proposal was found to yield more accurate and reliable results in terms of the average resistance ratio, accuracy across the whole range of the relative tube slenderness ratio and the calculated reliability index.