CALCULATION OF SHEAR BEARING CAPACITY, SLIP AND STIFFNESS OF HEADED STUDS IN STEEL-UHPC COMPOSITE SLAB

Steel-Ultra-high performance concrete (UHPC) composite slab has many applications in long-span bridges, in which the headed stud connectors play a key role. To explore the shear resistance of headed studs in steel-UHPC composite slab, six push-out specimens of headed stud were carried out, and different calculation methods were evaluated based on the test results, including six methods to calculate the shear bearing capacity, five models to predict the shear slip, and ten methods to calculate the shear stiffness. The test results show that the headed studs in all specimens appeared to break at the junction of the weld root, and the UHPC slabs remain intact except for partial damage at the root of the studs. The shear-slip curves of headed stud were divided into three stages, i.e., the elastic stage, the elastic-plastic stage and the descending stage. The maximum slip of all specimens is less than 3.5 mm, and the limit of elastic slip can be taken as 0.1 mm. The results show that the calculated shear resistance of headed stud in UHPC was lower than the test results according to some specifications without considering the contribution of stud welds. It is recommend that the stud welds contribution coefficient can be taken as 1.1 on the basis of the results of 2 sets of tests in this research and 29 sets of other effective data. The prediction results of different shear-slip models were different from the test results. It is suggested that the inverse proportional function model should be used to achieve accurate prediction. The actual force state of stud was not considered in the calculation of shear stiffness, resulting in significant difference in the calculation results. It is recommended that the shear stiffness corresponding to the slip of 0.1 mm can be taken as the elastic shear stiffness. The relationship between the shear-slip model and the shear stiffness of headed stud was established to provide a reference for calculation without test data.