Effects of concrete gap imperfection on axial compression behavior of CFREHS tubular T-joints

The concrete-filled round-ended elliptical hollow steel (CFREHS) tube have been gradually applied for bridge arches and truss structures in recent years, while concrete gap imperfections may be observed in these composite members due to the disadvantages resulted from the construction process, the service environment and the material defects. In order to explore the effects of gap imperfections on the performance of CFREHS tubular T-joints, ten CFREHS tubular T-joints were designed in this study. The effects of various parameters including the concrete gap ratio, joint intersection type and brace/ chord diameter ratio on the failure patterns, axial load bearing capacity, stiffness and ductility were analyzed, and the strain distribution rule and typical loading characteristics were revealed. The calculation models on the axially loading partition of steel brace and the flexural resistance of CFREHS chord were established based on the component method and failure mechanism of the joints. The design formulae for assessing the axial load bearing capacity of CFREHS tubular T-joints were presented considering the influence of concrete gap imperfections. The results indicate that the concrete gap imperfections would impair the axial load bearing capacity and stiffness of the CFREHS tubular T-joints, and the axial load bearing capacity and stiffness of the joints decrease with the gap ratio. Because of the effects of concrete gap imperfections and axial forces, the failure modes of this type of tubular joints include local buckling of brace, inward buckling of chord and the excessive deflection of chord. The design formulas can predict the axial load bearing capacity of the CFREHS tubular T-joints with concrete gap imperfections properly. © 2022 Science Press. All rights reserved.