Behavior of circular concrete-filled double-skin aluminum alloy tubular stub columns: Test, modeling and confinement-based design

Abstract

Concrete-filled double-skin steel tubular members have been widely adopted in marine structures, thereby being constantly subjected to harsh corrosive environment. This has triggered the emergence of concrete-filled double-skin aluminum alloy tubular (CFDAT) members of late, wherein aluminum alloy tube is taken as an excellent corrosion-resistant material. Nevertheless, the design guidelines of CFDAT columns have not yet been incorporated into existing international standards due to the absence of relevant research, hindering their structural applications. To this end, this study aims to further investigate the behavior of circular CFDAT stub columns under concentric loading and to clarify the confinement mechanism of this member. In total, 12 CFDAT stub columns were axially tested and the corresponding experimental results were discussed. The research findings showed that the ultimate load of CFDAT specimens is significantly affected by the hollow ratio, concrete strength and diameter-to-wall thickness ratio of outer tube. Using the test results, finite element (FE) model was developed and then utilized to ascertain the confinement mechanism of CFDAT columns, followed by a comprehensive parametric study of such members. Subsequently, the feasibility of current design formulas for the design of CFDAT columns was evaluated against the experimental results and outputs of FE analysis, accompanied by an obvious prediction deviation. Accordingly, a new confinement coefficient reflecting the confinement effect of concrete strength in such members was suggested, which can reasonably capture the interaction between of aluminum alloy tubes and sandwiched concrete. Using this coefficient, a unified design model for estimating the ultimate load of CFDAT and CFAT members was suggested and has better predictive ability than existing design codes and empirical formulas.