Evaluation on Shear Strengths of Single High-Shear Ring Anchors

The usage of anchors has increased in joints of new and old concretes for the purposes of seismic retrofits, remodeling, strengthening of existing structures, and so on. In most cases, the shear capacities of the anchors are governed by the steel strength of anchor rods. A lot of anchors should be installed to develop full strength of new structures. In this study, high-shear-capacity ring anchors consisting of steel ring and rod were developed and their shear capacities were examined through shear tests with varying beam width, concrete compressive strength, embedment depth of anchor rod, ring shape, epoxy types, and anchor types. For the specimens with the shallow width that is less than 3.33 times of the ring diameter, splitting failures occurred with the side cover concrete spalling. In splitting failure, the shear capacity increased as the specimen width increased. For the specimens with the wide width, the ring anchors failed due to bearing and the width did not affect the shear capacity. The shear capacities of the ring anchors are at least 1.75 times and up to 4.37 times of the shear capacity of the rod anchor. In addition, the ring anchors had higher stiffness and in most cases the maximum capacities were developed at 2 mm or less displacement. The improved stiffness may enhance the usage of the ring anchors for seismic retrofits. The embedment depth also affects the shear capacities of the ring anchors. With an embedment depth of 125 mm, the ring anchors have shear capacities of at least 3.3 times of the shear capacity of the rod anchor. Therefore, the number of anchors can be significantly reduced.