Performance of stud shear connections under combined shear and pull-out forces

This paper examines the structural behaviour of stud shear connections in solid concrete slabs under combined shear and pull-out forces. Nonlinear numerical simulations and parametric assessments are carried out using advanced finite element models which are validated and calibrated against detailed experimental results. Through realistic representation of yielding and ductile damage of the steel stud, as well as cracking and crushing of the surrounding concrete, the local 'stress and strain' conditions are evaluated and the underlying load transfer mechanisms within such connections are identified. It is found that the predicted resistance of the stud con-nections under shear forces in solid concrete slabs of various concrete grades compare favourably with codified design values. Importantly, however, it is shown that the corresponding shear resistance of these connections under various combinations of shear and pull-out forces exhibits a nonlinear reduction with the increase in the pull-out forces. The reduction in shear resistance of these connections reaches typically 15% to 20% for various concrete grades when a pull-out force of about 0.27 of the applied shear force is present. Based on the numerical results of the calibrated models, the effects of pull-out forces on the shear resistance of these connections are established and quantified. An interaction relationship for practical combinations of shear and pull-out forces for connections with various concrete grades is also proposed for design.