Design of Concrete-filled High Strength Steel Tubular X-joints subjected to Compression

Abstract

Design of concrete-filled high strength steel tubular X-joints subjected to compression is examined. A numerical investigation on concrete-filled high strength steel square and rectangular hollow section X-joints is presented in this paper. The high strength steel tubes had nominal yield stresses of 700 and 900 MPa. The infilled concrete had nominal concrete cylinder strengths of 35 and 100 MPa. A finite element model was developed and validated against test results. On validation of the finite element model, a parametric study comprised 156 finite element analyses was undertaken using the validated model. The strengths of the concrete-filled high strength steel tubular X-joints obtained from the parametric study together with available test results in the literature were compared with the nominal strengths calculated from the CIDECT Design Guide. It is shown that the CIDECT design predictions exhibited significant scatter and generally conservative for the concrete-filled high strength steel tubular X-joints. However, the CIDECT predictions overestimated the strengths of the concrete-filled high strength steel tubular X-joints with chord sidewall slenderness ratio exceeded 50. Hence, new design rules are proposed for concrete-filled high strength steel square and rectangular hollow section X-joints subjected to compression. It is shown that the proposed design rules are able to provide reasonably good predictions.