Experimental Research on Hysteretic Properties of Partially Encased Steel- Concrete Composite Beams

To investigate the hysteretic properties of the partially encased steel-concrete composite beams (PEC beams), combined with test data of previous studies,two PEC beams with different section heights under cyclic bending-shear loading were conducted. The results showed that under cyclic bending-shear loading, the failure mode of the PEC beams was tensile fracture at the steel flange of beam ends after elastic-plastic buckling, and the tensile fracture of the steel web accompanied by compressive collapse of concrete. The test values of the flexural capacity of PEC beams were about 10% to 30% larger than the corresponding values calculated by the full-section plastic method recommended by code T/CECS 719-2020, and the actual shear capacity of PEC beams was significantly higher than the theoretical calculation value. Concrete and links had good buckling-restrainted effect on flanges and webs of the main steel members. When the width-thickness ratios of the flanges and the spacing between the links obviously exceeded the limit range specified in code T/CECS 719-2020, the main steel member still achieved full-section plasticity, and the high strength advantage of steel was fully utilized. As for the two PEC beams, the hysteresis curves were full, the ductility coefficients were 4 and 6.8 (larger value for the beam with the higher section), and the average energy dissipation coefficients of the two specimens after yielding were about 2.2, indicating that the seismic performances of PEC beams were good.