Behavior of Concrete Expansion Anchors subjected to Installation Torque and Vertical Loading

The structural integrity and adequate behavior of anchors are important for the proper function of systems and components fixed by them subjected to seismic loading, pipe rupture loading and other design basis or beyond design basis loadings. Torque-controlled expansion anchor is most frequently used type of post-installed anchors, which is set by the expansion of one or more sleeves or other elements against the sides of the drilled hole through the application of torque. A structural analysis was carried out focusing on the behavior of torque-controlled expansion anchor under installation torque and vertical tensile loading according to slip conditions between components of the anchor and loading conditions. Based on the analysis results, it is confirmed that follow-up expansion is only possible when the friction resistance between the cone and the expansion sleeve is less than the friction force generated between the sleeve and the sides of the drilled hole. For the cases that the follow-up expansion does not occur, the pull-out resistance of the anchor increases with higher installation torque