Load transfer mechanism of an unwelded, unbolted, grouted connection for prefabricated square tubular columns under axial loads

This study develops a novel unwelded, unbolted, ultrahigh-performance fibre-reinforced concrete (UHPFRC) grouted connection for prefabricated square tubular composite columns. Herein, eight full-scale columns with UHPFRC grouted connections are tested to investigate their ultimate tensile and compressive resistance. The test results show that the novel connections exhibit good tensile and compressive resistance and structural stiffness. The primary failure modes are punching shear of the end plate, welding fracture at the inner tube, tube yielding and local buckling of the steel tube. The test specimens are simulated using finite element (FE) analysis in ABAQUS. The experimental and simulated results are in good agreement, indicating that the FE simulations can capture the observed failure modes and ultimate tensile and compressive resistance. Thereafter, existing analytical design formulas are evaluated to assess their suitability to predict the compressive and tensile resistance of prefabricated tubes with/without the novel grouted connections. A good agreement between the formula predictions and the test results are observed. These analytical formulas have the potential to be used in the design of the novel unwelded, unbolted, UHPFRC grouted connections for prefabricated steel, reinforced concrete and steel-concrete composite columns.