Analytical study on the tensile stiffness of headed stud connectors

In the theoretical or numerical analysis of composite/hybrid structures, headed stud connectors at the steel–concrete interface are usually modelled as linear spring elements; thus, their tensile stiffness will be an essential parameter to affect the tensile force distribution. This article investigates the tensile stiffness of headed stud connectors through theoretical analysis combined with the existing pull-out test results. The pull-out displacement of headed stud connectors from concrete blocks mainly includes two parts: one part is the elastic elongation of the stud rod and another is the axial displacement of the stud head in concrete blocks resulted from the concrete elastic deformation. Mindlin’s solution is employed to predict the second part displacement with the introduction of an unknown coefficient, which is estimated based on the existing headed anchor pull-out test results. Subsequently, an equation for predicting the tensile stiffness of headed stud connectors is proposed. The predicting tensile stiffness for headed stud connectors with various stud heights presents a good agreement with the pull-out test results. Meanwhile, neglecting the axial displacement of the stud head in concrete blocks, especially for relatively short height headed studs, will produce an overestimated tensile stiffness