Experimental Investigation of Concrete-Filled High-Strength Steel Tubular X Joints

© 2018 American Society of Civil Engineers.This paper presents an experimental investigation of concrete-filled high-strength steel tubular X joints. The high-strength steel tubes were cold formed into square and rectangular hollow sections with nominal 0.2% proof stresses of 700 and 900 MPa. The cold-formed high-strength steel tubes were infilled with normal and high-strength concrete with nominal concrete cylinder strengths of 35 and 100 MPa, respectively. A total of 31 tests was conducted, covering chord sidewall slenderness ratios varying between 12.6 and 40.6. Two different types of load-deformation behavior were observed and are discussed in this paper. The obtained test strengths were compared with the nominal strengths calculated using Comité International pour le Développement et l'Étude de la Construction Tubulaire (CIDECT) design provisions. Overall, the nominal strengths predicted by the CIDECT design provisions are quite conservative for concrete-filled high-strength steel tubular X joints with chord sidewall slenderness ratios up to 40. However, the predictions for specimens with ductile load-deformation behavior are found to be overly conservative. Hence, modifications to CIDECT provisions are suggested for the design of concrete-filled high-strength steel tubular joints under transverse compression.