Tightening Torque Influence on Pullout Behavior of Post-installed Expansion Anchors

Post-installed anchors in reinforced concrete structures are increasingly important in current constructions especially in repair or upgrading works. A research program was completed to determine the influence of the tightening torque and the anchorage depth on the pullout performances of torque-controlled expansion anchors. The diameter d of the tested anchors was 10 mm. Six configurations were tested on 18 concrete blocks. Three pre-tension loads and two anchorage depths were considered. The results show that the fastening torque has no influence on the load-bearing capacity far away from the edges. However, an increase of the torque leads to a decrease of the anchor’s slipping during pullout tests. Nevertheless, applying an excessive fastening torque may lead to a steel-rupture of the anchor during the fastening phase. An increase of the anchorage depth leads to a better load capacity of the anchor and reduces the risk of concrete cone rupture. Finally, a simplified model of the tension response of the anchor with a bilinear load-displacement relationship has been suggested.