Study on the bonding behavior of concrete-filled aluminum alloy tube

Aluminum alloy has been widely used in modern engineering structures due to its good corrosion resistance, light-weight, convenient processing, and recyclability. To study the bonding behavior of concrete-filled aluminum alloy tubes (CFAT) columns and obtain the bond strength formula and bond-slip constitutive model of CFAT, the push-out tests of three circular and three square CFAT specimens were conducted. The failure patterns, load-slip/strain curves and the stress distribution of the stubs were investigated. The results show that the longitudinal strain of both square and circular CFAT specimens increased from the loading end towards the free end. Based on the elastic assumption, the interfacial bond stress of CFAT was calculated. The ultimate bond strength for the circular specimens ranged from 0.77 to 1.77 MPa, whilst the square ones ranged from 0.22 to 0.51 MPa. As the section size increased, the bond strength of CFAT gradually decreased. When the diameter-to-thickness ratio or the width-to-thickness ratio increased from 48.0 to 80.0, the ultimate bond strength of the square and circular specimens decreased by 67.2% and 67.5%, respectively. Additionally, a calculation formula for the ultimate bond strength of CFAT is proposed. Based on the proposed formula for characteristic points, a bond-slip constitutive model for CFAT columns is proposed and validated. Finally, based on the verified bond-slip constitutive model of CFAT, the finite element (FE) models of spring element and cohesive model are established, respectively. The modeling result of the spring element is more accurate and the calculation efficiency is higher. However, the modeling process is complex.