Tensile behavior of improved CFRP-square hollow steel tube composite member strengthened with thick-walled steel tube

Abstract

An improved CFRP-square hollow steel tube (CFRP-SHST) composite member strengthened with a thick-walled section at each end of the steel tube was proposed to prevent premature debonding of CFRP. The square hollow section (SHS) steel tube in the proposed composite member is composed of two thick-walled SHS at both ends and a thin-walled SHS at the center. The test of six proposed CFRP-SHST composite member specimens and one conventional CFRP-strengthened equal-thickness SHS composite member specimen under axial tension load was carried out. Test results indicated that the proposed CFRP-SHST composite member had a better bonding performance, as well as higher ductility than the conventional composite member due to the presence of the thickened sections. The failure mode was the exterior CFRP rupture and interfacial debonding near the end section of the loading side for the improved composite member. Besides, finite element analysis (FEA) was developed to investigate the interfacial stress distribution and the evolution of adhesive layer damage. In addition, a simple calculation approach for tensional carrying capacity was proposed, which was verified by test results.