SHEAR PERFORMANCE OF MULTI-STUDS BETWEEN STEEL TUBE AND CORE CONCRETE

Concrete-filled steel tubular (CFST) specimens with multi-row and multi-column studs were designed for push-out tests, including 6 specimens with studs and 1 specimen without studs. Key experimental parameters involved the circular space, the longitudinal space and the amount of rows of studs. In the meantime, the finite element analysis software, ABAQUS, was used to simulate the CFST push-out test. The numerical results coincide well with the experimental results. The test results and numerical analysis show that the load-slip curve of the specimen with multi-studs consists of linear elastic stage, elastic-plastic stage, load descent stage and load residual stage. Along the loading direction, the concrete stress at the back of the stud is 50.1 MPa~68.8 MPa, exceeding the cylinder compressive strength ( ƒ_c'= 50.1 MPa), so that the concrete deforms greatly. Mises stress in root is the largest in all studs. The root part reaches the ultimate strength first and then cut off. The average shear bearing capacity of one stud decreases with the decrease in the circular space, longitudinal space and the increase of rows. The computational formulas of three reduction coefficients are proposed. To make full use of the shear performance and avoid concrete crack before stud, the circular and longitudinal spaces should not be less than 3.4 and 4.4 times the stud diameter, respectively. The analysis results indicate that the three factors: the circular space, longitudinal space and the amount of rows are mutually independent. The shear bearing capacity reduction factor can be expressed as the multiplication of the three reduction coefficients.