EXPERIMENTAL STUDIES ON SHEAR-BEARING CAPACITY OF HEADED STUD IN CONCRETE-FILLED STEEL TUBE

Headed studs attached to the internal face of the steel tube of concrete-filled steel tubular(CFST) components enhance the composite effect between steel tube and core concrete. Testing of 8 CFST specimens with headed studs was conducted, considering the primary variables core concrete strength, diameter and length of headed studs, and the results compared with 1 CFST specimen without headed studs and 4 composite beam specimens with headed studs. The results show that the load-slip curve of a CFST specimen with headed studs consists of a linear elastic stage, an elastic-plastic stage, a load descent stage, and a load residual stage. The headed studs were sheared off at the peak load while no fracture or crushing of concrete had occurred and the stress in the steel tube was very low. The ultimate load of CFST specimens with headed studs were 673.3 kN~1356.9 kN, much higher than the 85.7 kN of the specimen S4-1 without headed studs, which shows the obvious improvement from the headed stud on the composite action of the steel tube and core concrete after debonding between them. No separation between core concrete and steel tube was observed in the test of the CFST specimens with headed studs, which resulted full utilization of the headed studs and 1.69~1.73 times as much ultimate bearing capacity as the composite beam specimens with headed studs. The shear-bearing capacity of headed studs in CFST increases with increasing core concrete strength and stud diameter, but it is little affected by stud length. Based on the analysis on experimental results, a formula to predict the shear-bearing capacity of headed studs in CFST is proposed.