Challenges and design enhancements on fatigue performance of post-installed anchors

Post-installed anchors are widely used in structural applications and often subjected to cyclic actions requiring fatigue verification according to EN 1992-4. Steel failure in the thread is the dominant fatigue mode, which is strongly influenced by manufacturing processes and static load level. While EN 1993-1-9 provides fatigue categories for bolts and rods (FAT 50 in tension, FAT 100 in shear), experimental evidence shows that threaded anchors in shear are penalised by concrete interaction, bending stresses and thread location in the shear plane. This review synthesises experimental and analytical studies, comparing outcomes with current design provisions. For tension loading, FAT 50 remains applicable. For shear one, test data consistently fall below FAT 100, with a mean fatigue strength of 89 MPa at 2 × 106 cycles, justifying a reduced category of FAT 71 (m = 5). A noise barrier case study demonstrates that ungrouted stand-off configurations increase peak anchor stresses by ~35% compared to direct base-plate contact, resulting in principal stress ranges that are incompatible with current code provisions for realistic service loads. On this basis, anchor-specific fatigue categories are proposed: FAT 50 for tension (confirmed), FAT 71 for shear, and eccentricity-dependent factors for bending-dominated loading. These recommendations address critical gaps in EN 1993-1-9 and EN 1992-4, enabling a safer design for stand-off connections currently outside the scope of the code.