FEM analysis on failure development of group studs shear connector under effects of concrete strength and stud dimension

Group studs, arranging studs in group, has been applied as shear connectors in steel and concrete composite structures for over 50 years. Concrete strength and stud dimension are the crucial factors affecting the failure appearance of shear studs in push-out test, which mainly consists of stud shear fracture, stud bending deformation and local concrete crush. Since the detailed failure development has rarely been concerned, a parametrical push-out FEM analysis with damage plasticity models on failure development of group studs with effects of concrete strength and stud dimension was executed. In this study, concrete compressive strength of 30 MPa, 40 MPa and 50 MPa, shank diameters including 13 mm, 16 mm, 19 mm and 22 mm and stud heights including 80 mm and 100 mm were the parameters. In general, it was found that when under effect of concrete strength, shear stiffness of stud with large shank diameter performed more stable while its shear strength may be influenced more apparently. Meanwhile, the analyzed concrete damage, stiffness degradation and ultimate deformation of stud were discussed as well. The failure development of push-out model was reflected by the development of equivalent stud bending arm in terms of shear transfer between steel and concrete through studs, which experienced three steps due to the degradations of concrete and stud modulus. It also shows that models with lower concrete compressive strength or more flexible stud in combination with high concrete strength can lead to relatively obvious stud bending deformation.