Failures in concrete-filled steel tubular joints due to cyclic loading

SHSs are widely used in engineering structures that are subjected to different types of loads, such as bridges, communication towers and offshore platforms. CFSHSs are used in large-span bridges. In steel tubular structures, CFSTs are used as main members as they show high stiffness, strength, and ductility. The SHS T-joint connections with concrete-filled chords will generally have lower SCFs compared to empty SHS T-joints. The hot spot locations of SHS-SHS T-joints occur at lines A–E. Experimental and numerical investigations on empty and concrete-filled SHS T-joints under different load cases were carried out. For the experimental investigation, strain gauges were installed onto the SHS-SHS T-joint connections to determine the SCF at the hot spot locations (lines A–E). The numerical investigation was carried out by developing 3D FE T-joint models identical to the experimental T-joint specimens using Abaqus FEA software to capture the distribution of the SCF and calibrate the results. Design formulae for predicting the SCFs of empty SHS-SHS T-joints under out-of-plane bending were proposed. Furthermore, design formulae for predicting the SCFs of concrete-filled SHS-SHS T-joints under in-plane bending, out-of-plane bending and tension on the brace were proposed. The design graphs and formulae to facilitate the determination of SCFs will prove to be an important component of the upcoming CIDECT fatigue design guide and will contribute to fatigue design and better inspection of existing bridges and tubular structures