ABSTRACT
Shear strengthening of existing structures is a rather difficult task with respect to the short available anchorage length in the structural member and the target of reasonable activation of the strengthening element before the rather brittle shear failure takes place. In order to overcome such technical requirements, an innovative undercut anchor was developed. The anchors are set into predrilled holes from the soffit of a structure and, via application of a torque moment, slightly pre-tensioned. The undercut solution provides a very short and effective anchorage inside the concrete, and applying a torque moment already activates the system during installation. Large-scale tests on 5.4 m long T-beams designed for shear failure have been performed to verify the functioning of such strengthening solution. All tests ended up in shear failure, with nearly full utilization of the post-installed anchors and load gains around 40% with four and 90% with seven rods.
