Performance Evaluation of Torque-Controlled Expansion Anchors with Improved Sleeve and Header Details

This study assesses improvements in the head and extension sleeve parts for a post-installed anchor. The sleeve and head details were proposed to enhance the structural performance of the post-installed anchor, and the optimal structural shape was determined through finite element analysis. The analysis results revealed that the anchor's performance was most efficiently improved when the sleeve length was 9.0 mm and the head length was 3.0 mm. In the model with these dimensions applied, the performance improved approximately 1.71 times compared to the existing model, validating the effectiveness of the proposed structural details. The improved pull-out strength test of anchor diameter M12 showed an increase of 1.25 times in normal-strength concrete and 1.28 times in high-strength concrete, with an embedded depth of 50 mm. The improved pull-out strength test of anchor diameter M16 showed that the pull-out strength increased by 1.42 times for normal-strength concrete and about 1.33 times for high-strength concrete. This research proposes a modified equation that reflects changes in the effective embedded depth and diameter. A comparison of the proposed equation with that of European Technical Approval Guideline (ETAG) showed that the correlation coefficient changed from 0.908 to 0.962, and the coefficient of variation changed from 18.9 to 10.4%, meaning that the proposed equation reflected the actual experimental values more accurately.