Experimental investigation on axial local compressive behavior of square concrete-filled double tubular stub columns

Abstract

This paper investigated local compressive behavior of square concrete-filled double tubular (CFDT) specimens. A total of twenty-nine specimens were tested under axial local compression to study the influence of the inner tube, bearing block shape, local compression area ratio, outer steel tube thickness, concrete strength, and steel strength on the local compressive bearing capacity of specimens. The working mechanism of CFDT under local compression was analyzed. The results show CFDT specimens exhibit superior bearing capacity and ductility, compared to conventional CFST specimens. The larger confinement effect coefficient ξ or local compression area ratio β can delay the appearance of the descending stage of N - Δ curve and improve the ductility of the specimen. The increasing degree of bearing capacity is related to β. When β = 2.25, the most effective measure is to increase the thickness of the outer tube, up to 36.8 %. When β = 9, the use of high-strength concrete is more conducive to improving the bearing capacity, up to 21.8 %. The shape of bearing block has little effect on the bearing capacity. In addition, finite element model was established and analyzed based on experimental results, reasonably agreement was obtained between numerical and measured results. An evaluation method for calculating the local bearing capacity were proposed, which showed good consistency with experimental results.