Numerical Study on the Tensile Performance of Headed Stud Shear Connectors with Head-Sectional Damage

An extensive numerical study was carried out due to the concern that head-sectional damage caused by corrosion poses a threat to the tensile performance of headed stud connectors. Three-dimensional finite element models of pull-out tests were established, with both material and geometric nonlinearities being considered. In particular, the concrete weak region due to bleeding was simulated. The simulation method was verified by the results of pull-out tests on two connectors with different damage degrees. Tensile performance of headed stud shear connectors of various shaft diameters (d_s = 10 to 25 mm) with various damage degrees (up to 50%) was simulated. It was observed that the connector with a high damage degree exhibited low capacity and a failure closer to pull-out failure than concrete cone breakout failure. Based on the numerical results, reduction factors for quantitatively assessing the influence of head-sectional damage degree on the loading capacity and stiffness of connectors were proposed. With reference to the Concrete Capacity method, the reduction in tensile capacity of connectors with head-sectional damage was found to be caused by the decrease in the projected area of the concrete cone due to the reduction in head diameter, concrete cone angle, and embedment depth. Meanwhile, numerical results showed that the stiffness of a connector at a high embedment depth or in high strength concrete was more sensitive to head-sectional damage. It was also found that the elastic modulus of the weak region significantly affected the stiffness of connectors, while the influence of its thickness on the capacity and stiffness was insignificant.